Update change log and prepare v30r4 release notes

CHANGELOG.md

 # Changelog
 All notable changes to this project will be documented in this file.
 
-Project Coordinators: Marco Clemencic, Charles Leggett, Benedikt Hegner
+Project Coordinators: Marco Clemencic, Charles Leggett
 
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased][]
 
 ### Changed
+- Reorganization of Gaudi::Parsers code ([mr !759][])
+- Update LCG to 94 and Gaudi version to v30r4 ([mr !776][])
+- Update minimum required CMake version to 3.6 ([mr !789][])
+- Remove m_event_context from `Algorithm` ([mr !784][])
+- Reimplementation of DataHandle ([mr !462][])
+- Improve extension API in `EventContext` ([mr !770][])
+- Change return type of interger counters operations, like _mean_, to float ([mr !786][], [issue #50][])
+- Clean up `IDataProviderSvc` and `IDataManagerSvc` interfaces ([mr !674][])
+- Avoid printing empty counters ([mr !777][])
 - Use `unique_ptr` for `EventContexts` ([mr !732][], [issue #37][])
 - `ConcurrencyFlags`: move setting from `AvalancheScheduler` to `HiveWhiteBoard` ([mr !726][])
 - Introduce a generic `IDataStoreAgent` implementation ([mr !661][])
@@ -15,12 +24,23 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Adding actual type of object in data store to error messages ([mr !715][])
 
 ### Added
+- Add `Gaudi::Property` constructors which accept an update handler ([mr !769][])
+- Optionally capture and print exception backtrace ([mr !653][])
 - Add build and runtime support for gcc/clang sanitizers ([mr !744][])
 - Add debug builds to Gitlab-CI and other improvements to CI configuration ([mr !756][])
 - Introduce `IDataBroker` interface, and `HiveDataBroker` implementation ([mr !685][], [mr !739][])
 - Added an accumulate helper function to new counters ([mr !717][])
 
 ### Fixed
+- `HiveWhiteBoard::freeStore`: check whether slot was already free ([mr !779][], [issue #49][])
+- Fix segfault when scheduling `EventViews` ([mr !781][])
+- Fixed bug in `BinomialCounter` when using buffer ([mr !764][])
+- Clarify scalar `operator()` signature in `MultiScalarTransform` ([mr !755][])
+- Fix potential race condition in `TimelineSvc` ([mr !750][])
+- Implicitly convert `DataObjectHandleBase` to `str` properties ([mr !773][])
+- Filter out install and build files from `make apply-formatting` ([mr !747][], )
+- Fixed issues reported by gcc/clang sanitizers ([mr !749][], [mr !757][], [mr !758][], [mr !752][], [mr !751][], [mr !746][], [mr !772][], [mr !753][])
+- Make sure a test fails if its reference file is not found ([mr !734][])
 - Fix Floating Point Exception in `counters.h` ([mr !760][])
 - Make the CMake tests more resilient to symlinks ([mr !742][])
 - Add support for versioned ROOT libraries ([mr !737][])
@@ -36,8 +56,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added correct `vector_of_const_::operator[]` and ::at ([mr !710][])
 
 ### Clean up
+- Fix some gcc 8 warnings ([mr !782][])
+- Remove unused mutex member in `Algorithm` ([mr !767][])
+- Replaced invalid `std::forward` with `std::move` in `PluginService` ([mr !745][])
 - Counters: improve doxygen ([mr !754][])
-- Minor code clean up ([mr !408][])
+- Minor code clean up ([mr !408][], [mr !740][], [mr !774][])
 
 
 ## [v30r3][] - 2018-08-01
@@ -136,14 +159,43 @@ Details about old versions of the project can be found in the
 [ReleaseNotes](ReleaseNotes) folder and in the `release.notes` files in
 [GaudiRelease/doc](GaudiRelease/doc).
 
+[mr !789]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/789
+[mr !786]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/786
+[mr !784]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/784
+[mr !782]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/782
+[mr !781]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/781
+[mr !779]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/779
+[mr !777]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/777
+[mr !776]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/776
+[mr !774]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/774
+[mr !773]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/773
+[mr !772]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/772
+[mr !770]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/770
+[mr !769]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/769
+[mr !767]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/767
+[mr !764]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/764
 [mr !760]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/760
+[mr !759]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/759
+[mr !758]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/758
+[mr !757]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/757
 [mr !756]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/756
+[mr !755]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/755
 [mr !754]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/754
+[mr !753]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/753
+[mr !752]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/752
+[mr !751]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/751
+[mr !750]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/750
+[mr !749]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/749
+[mr !747]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/747
+[mr !746]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/746
+[mr !745]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/745
 [mr !744]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/744
 [mr !742]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/742
+[mr !740]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/740
 [mr !739]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/739
 [mr !738]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/738
 [mr !737]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/737
+[mr !734]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/734
 [mr !733]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/733
 [mr !732]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/732
 [mr !731]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/731
@@ -185,6 +237,7 @@ Details about old versions of the project can be found in the
 [mr !677]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/677
 [mr !676]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/676
 [mr !675]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/675
+[mr !674]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/674
 [mr !673]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/673
 [mr !672]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/672
 [mr !671]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/671
@@ -204,6 +257,7 @@ Details about old versions of the project can be found in the
 [mr !656]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/656
 [mr !655]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/655
 [mr !654]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/654
+[mr !653]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/653
 [mr !652]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/652
 [mr !651]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/651
 [mr !650]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/650
@@ -219,9 +273,12 @@ Details about old versions of the project can be found in the
 [mr !604]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/604
 [mr !594]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/594
 [mr !526]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/526
+[mr !462]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/462
 [mr !448]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/448
 [mr !408]: https://gitlab.cern.ch/gaudi/Gaudi/merge_requests/408
 
+[issue #50]: https://gitlab.cern.ch/gaudi/Gaudi/issues/50
+[issue #49]: https://gitlab.cern.ch/gaudi/Gaudi/issues/49
 [issue #37]: https://gitlab.cern.ch/gaudi/Gaudi/issues/37
 [issue #36]: https://gitlab.cern.ch/gaudi/Gaudi/issues/36
 [issue #27]: https://gitlab.cern.ch/gaudi/Gaudi/issues/27