DE12: Restructure IFileGroupMgr.java to be more readable 
https://rally1.rallydev.com/slm/detail/df/19347564882

Hide the newGroup() method so it's no longer publically accessible.
DE12: Restructure IFileGroupMgr.java to be more readable 
https://rally1.rallydev.com/slm/detail/df/19347564882

Reorder the methods in IFileGroupMgr/FileGroupMgr, and add banners to
make it easier for the reader to see which methods apply to which type
of file group.
IN-PROGRESS - task US2: Export file groups from packages 
https://rally1.rallydev.com/slm/detail/ar/18901923777

This work is incomplete, but needs to be shared on GitHub.