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