Improve the CMS example. Add word for the raw generator status of generator particles to Geant4Particle

 - add all parentless particles to outgoing vertex

if the hit is produced by a particle that is not kept in the MCParticle history we set the bit
added originalG4ID to Geant4Particle class for faster lookup, as this ID is stored with the hit
Otherwise we need a complicated and time-consuming logic to parse the equivalent map if this hit really belonged to that track

Add test to dump hits from MultiSegment-MultiCollections example. Investigate issue: https://github.com/AIDASoft/DD4hep/issues/141 for details

 - changed signature of Geant4EventReader::readParticles(int,Vertex*, Particles&)
   to Geant4EventReader::readParticles(int,Vertices&, Particles& )
 - implement in LCIOEventReader, Geant4EventReaderHepEvt and Geant4EventReaderHepMC
 - for now still one vertex only is created using the first final state particle
   for HepEvt and LCIO

   - note: this does not yet seemt to be filled by DDG4!

Add DDRec/src/plugins to folders documented by doxygen

Add groups for plugins and some example
Add an entry in the main "Modules" part of the doxygen website so they are easily found.
And sub groups for different plugin types.
See changes in the plugins for example. The documentation in these changes is not complete.

Clearer status message in moveToEvent functions, change verbosity for particle printout in HepMC, add comment

use m_currEvent everywhere
move skipEvent logic to moveToEvent

Use moveToEvent function which is called in InputAction
use m_currEvent part of base EventReader class instead of redefining it
Increment m_currEvent in local function to be next to call to reader->readEvent instead of calling in the function calling readParticleCollection

Support for multi-threaded Geant4 applications using DDG4Details are described in the release notes.

use map(string, string) to store parameter value pairs, declareProperty so we can pass it from python as a dict
call saveRun from endRun

  as using direct access always requires runNum==0 and sequential evt nums ...