Remove materials from LCDD. Look them directly up in the TGeoManager instance and avoid double caching.

 - changed to use standard way of finding geant4 with CMake:
   -D Geant4_DIR=_path_to_Geant4Config.cmake 
   (this script provies also the dependencies used to build geant4)

  - added Property $Id$ to all *.h *.cpp and *.xml files
    to allow versioning with SVN