Added metadata call to load the parents of FileAnnotations
Renamed 'Unlink' option to 'Remove'
Overhauled 'unlink' and 'delete' attachment options

Removed 'delete' option (attachments cannot explictely deleted anymore,
instead are deleted automatically when the last link is removed)
Renamed 'unlink' option to 'remove'
Added a proper warning dialog instead of using a Messagebox
Added some comments
Switched to HashMultimap
Fixed weird indents
Fixed wrong import
Fixed various minor things
Removed unneccessary code
Truncate long file names
Fixed "Remove ... by me / by others" bug
Just cleaned up the messy import statements of the previous commit again
Fixed indent
Merge pull request #2390 from dominikl/rebased/dev_5_0/remove_last_file_annotation

Remove last file annotation (rebased onto dev_5_0)