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
Bugfix: Weird behaviour after switching users

After switching user new service adapater instances were created but never
passed on to the registry.
Updated copyright date
Fixed "Remove ... by me / by others" bug
Just cleaned up the messy import statements of the previous commit again
Fixed indent
Merge pull request #2268 from dominikl/remove_last_file_annotation

Remove last file annotation