( use px_lay.attr<int>(_U(number)) rather than "number" ) 

 -  added release notes 

    - added gaseous volumes to force creation 
      of hits on the meassurement surfaces

  - fixed some debug output

   with air 

     combine all VolIDs from all parent volumes
     in the path to the current sensitive volume
    - used in Geant4CalorimeterSD and 
      Geant4TrackerSD

Add utility function to BitField64- Use BitField64 in the IDDescriptor class- Remove implossible lookup functions using PlacedVolumes from VolumeManager.

  
  - added new method:
    long long Geant4SensitiveDetector::getVolumeID(G4Step* step)
  
  - use it in Geant4Tracker(Calorimeter)SD
  
   - changed ILDExEventAction to extract the correct 
     readout string from lookup via cellID
 

    as we now have a standalone tool 
    for this: g4gdmlDisplay

     start with the least significant bit
     (the 'lcio' convention)
   - unused hight bits are still all 1
     this is 'cured' in BitField64.setValue() 

   => ideally we should try an use 0 as default value
      for the IDDescriptors and unused bits
      this would allow to directly use the 
      VolumeID of the sensitive volume as cellID
      for the hits
   ( I did not manage to get this working, though.)

   - using the VolumeID set for PlacedVolumes to be the
     superset of the physVolIDs of the complete 
     path from the world volume
     - as the internal encoding in DD4hep starts with
       the MSB we have to transfer it into the LC
       convention using the BitField64 class

     -> see code in Geant4TrackerSD
        ( should go to a standalone/utility function)
   
   - adopted VXD and SIT to set the complete
     set of the canoncial cellID: system,side,layer,module,sensor


--Ths lin, and those below, will be ignored--

M    DDG4/src/Geant4TrackerSD.cpp
M    DDExamples/ILDExDet/compact/ILDEx.xml
M    DDExamples/ILDExDet/src/compact/ILDExSIT_geo.cpp
M    DDExamples/ILDExDet/src/compact/ILDExVXD_geo.cpp

   in copyNrs

     of BitFields in the LC convention
     (starting with the LSB)
      

  - tried to change encoding (starting with LSB)
     did not work : commented out again

    RegularNgonCartesianGridXY needs gridSizeY and gridSizeZ (!)

  - updated AHcalBarrel driver (simplified geometry) (S.Lu)

   ./bin/ILDExSimu  -g ./ILD_toy.gdml
   - use as cross check with gdml files created by
     geoConverter
   - remove volid tags beforehand:
     cat ILD_toy.gdml | grep -i physvolid > ILD_toy_fixed.gdml