Improved rename

Made it more thorough and use the new InodeFolder structure.
Removed null check for getPath in rename
Created _rename method, which allows EditLog to replay rename without
logging
Fixed inner _rename method
Added comments for exceptions in _rename
Fixed _rename and added @throws to CommonUtils javadoc
Made rename return a boolean rather than throw exceptions
Merge pull request #184 from manugoyal/rename-improvements

Improved rename