- fixed retrieval of command line arguments
- refactoring of some platform specific code

Algorithms automatically retrieve their ToolHandles during initialize()
if they are enabled. ToolHandle::enable()/disable() methods added for
explicit control from C++. Alternatively, ToolHandles are disabled if
their name is an empty string.

See merge request !429

See merge request !465

See merge request !468

prepare_base and prepare_ext tests should not be run at the same time
because they use one shared output file (MultiInput.xml)

Use map<enum class,string> instead of unordered_map.

See merge request !453

See merge request !432

add missing header guard to invoke.h

See merge request !457

- restore use of recursive_mutex (required to avoid a deadlock
  in MiniBrunel)
- add method to IHiveWhiteBoard to explicitly register new items
  (will be needed by FetchDataFromFile)
- remove unused IHiveWiteBoard::newDataObjectsPresent()
- avoid OUT parameters & StatusCode, prefer to just return the OUT
  parameter
- fix comments

Fixed use of messages in ApplicationMgr::i_startup

See merge request !436

See merge request !447

Adding DecisionNode negation mapping the "Invert" parameter of the GaudiSequencer

Since the introduction of Phoenix v3 (in boost 1.47) the 'result'
struct is no longer needed in spirit parser. See eg.
http://www.boost.org/doc/libs/1_47_0/libs/phoenix/doc/html/phoenix/what_s_new/phoenix_3_0.html
which points out the switch to the 'Boost::Result_of' protocol

Modernize genconf

See merge request !437

and rename the variables used to iterate over the values returned to
indicate they are names of factories.

Also, remove some pre-C++11 compatibility scaffolding

- prefer enum over std::string
- prefer freestanding function in anonymous namespace over member
  functions
- prefer direct member initialization
- prefer auto
- prefer range-based for loops
- use std::type_index to compare std::type_info objects (the latter
  are not guaranteed to be unique for a given type!)
- prefer std::unordered_map over Gaudi::HashMap
- prefer std::vector<std::pair<std::string,std::string>> over
  Gaudi::HashMap if no lookup is required

fix formatting

See merge request !442

tweak overload resolution of TupleObj::farray  for  gcc7

See merge request !430

Fix task-based conditions handling

See merge request !431

Fix various printouts

See merge request !416

add TaggedBool

See merge request !435

update gitlab-ci.yml to use centos7

See merge request !433