Adds various impr. to the not. removal of entities

 * Fixes a problem where the ContentVersion's language name was not
   displayed for Content->Content references
 * Fixed a problem where all references from a Content was cleared when
   the user tried to only clear one (red cross symbol)
 * Changes the name of the force delete button in the reference views and
   adds an explanatory text instead so the user understand the effects of
   executing the action
Merge pull request #111 from stenbacka/notified-delete-improvements

Adds various impr. to the not. removal of entities