Changed DisplayPatients table schema: renamed MRN to PatientID; Added role headers in the CMakeLists file
Added empty names maps; Implemented getDisplayFieldsForInstance for the RT series description rule
Merge remote-tracking branch 'remotes/cpinter-commontk/276-dicom-database-display-tables' into 276-dicom-database-display-tables

Conflicts:
	Libs/DICOM/Core/ctkDICOMDisplayedFieldGeneratorAbstractRule.h
Fixed rules (still WIP)