updates and fixes to CMake build

- added build of examples
- use Geant4 sources from git (https://gitlab.cern.ch/lhcb/Geant4-srcs)

Merge branch 'master' of ssh://gitlab.cern.ch:7999/clemenci/Geant4

* 'master' of ssh://gitlab.cern.ch:7999/clemenci/Geant4:
  added entries to release.notes
  minor fix to handling of G4_NATIVE_VERSION
  use Geant4-srcs master for version HEAD
  do not use Ninja to buid Geant4 (not working)
  Get Geant4 sources from git instead of tarfiles
  fixed installation of Geant4 analysis headers
  install examples scripts and create "aliases" for commands
  removed 'Makefile's that should not be there
  Fixed build of the selected examples.
  updated copying of Geant4 sources to CMT directories
  added useful .gitignore files

See merge request !1


git-svn-id: svn+ssh://svn.cern.ch/reps/lhcb/Geant4/trunk@197133 4525493e-7705-40b1-a816-d608a930855b