CASTOR-4842 RFE: CASTOR 2.1.15-x should have a generic dismount command

castor/mediachanger/CMakeLists.txt

castor/mediachanger/DismountCmd.cpp

castor/mediachanger/DismountCmd.hpp

castor/mediachanger/DismountCmdLine.cpp

castor/mediachanger/DismountCmdLine.hpp

castor/mediachanger/DismountCmdMain.cpp

castor/mediachanger/MediaChangerFacade.hpp

castor/mediachanger/MmcProxyDummy.hpp

castor/mediachanger/MmcProxyLog.hpp

castor/mediachanger/MmcProxyNotSupported.hpp

castor/mediachanger/MountCmd.cpp

castor/mediachanger/castor-tape-mediachanger-dismount.man

castor/mediachanger/castor-tape-mediachanger-mount.man

debian/castor-tapeserver-server.install.perm

debian/castor-tapeserver-server.manpages