Added the UserGroup and VO classes

middletier/CMakeLists.txt

middletier/cta/ArchivalRoute.hpp

middletier/cta/ConfigurationItem.hpp

middletier/cta/DriveQuota.cpp

middletier/cta/DriveQuota.hpp

middletier/cta/LogicalLibrary.hpp

middletier/cta/MountCriteria.cpp

middletier/cta/MountCriteria.hpp

middletier/cta/StorageClass.hpp

middletier/cta/Tape.hpp

middletier/cta/TapePool.hpp

middletier/cta/UserGroup.cpp

middletier/cta/UserGroup.hpp

middletier/cta/VO.cpp

middletier/cta/VO.hpp