BRANCH 4.2:
  renamed free_copy as copy, free_move as move, and the default is "create" mode for file/directory/group checkin
  In ThumbCmd check for if extension is in normal file extension list. It was checking the path instead which is incorrect.
  made Config.get_value() tolerate a simple string config when sub_key is used.
  added support for copy directory in FileUndo.create()
BRANCH 4.2-DEV:
   adjusted file checkin copy mode
   added removed trailing . in Naming.naming_to_file() since Common.get_filesystem_name() doesn't do any processing in 4.2
4.2: Fixed sidebar manager bug - right click remove didn't work.4.2: Fixed sidebar manager bug - right click remove didn't work.
4.2: Fixed typo in last commit.