such that other user actions can access it (e.g. for adding the MCParticle collection)

    - renamed namespace tgeo to dd4hep
       -> users need to replace tgeo::mm by dd4hep::mm

 - protect against missing collections in test_surfaces

 - enforce usage of units from TGeoUnits.h in xml expression evaluators
 - convert to degrees for angles in TGeoShapes constructors
 - NB: there is one inconsistency left here:  angles returned 
       from TGeoShapes are already in degrees, this is the one
       case where a quantity returned from DD4hep/TGeo does not have the default
       units - thus one should not write
       double phi = coneSeg.Phi1() / tgeo::rad ;
       but rather
       double phi = coneSeg.Phi1() * tgeo::deg ; 
 

   for cylindrical surfaces

     virtual Vector2D globalToLocal( const Vector3D& point) const ;
     virtual Vector3D localToGlobal( const Vector2D& point) const ;
 - implementation in VolSurface/Surface for planes
 - added simple tests in  test_surface
 - to be done: cylinders ...

					-- Compuzius

include/DDSurfaces/Vector3D.h:212:11: error: ‘fabs’ is not a member of ‘std’

  - changed ISurface interface for u(),v(),normal() to return Vector3D 
    rather than const Vector3d&
  - added some documentation for Surface methods