Merge branch 'TRT_BaseElement_further_partIII' into 'master'

...T_ReadoutGeometry/TRT_ReadoutGeometry/TRT_BarrelElement.h

...ReadoutGeometry/TRT_ReadoutGeometry/TRT_BarrelElement.icc

...T_ReadoutGeometry/TRT_ReadoutGeometry/TRT_EndcapElement.h

...ReadoutGeometry/TRT_ReadoutGeometry/TRT_EndcapElement.icc

...DetDescr/TRT_ReadoutGeometry/src/TRT_BarrelDescriptor.cxx

...DetDetDescr/TRT_ReadoutGeometry/src/TRT_BarrelElement.cxx

.../InDetDetDescr/TRT_ReadoutGeometry/src/TRT_Conditions.cxx

...tDetDescr/TRT_ReadoutGeometry/src/TRT_DetectorManager.cxx

...DetDescr/TRT_ReadoutGeometry/src/TRT_EndcapDescriptor.cxx

...DetDetDescr/TRT_ReadoutGeometry/src/TRT_EndcapElement.cxx