Several changes:
 - Changed EditEvent so that it uses AJAX (added a partial view, EventSpecificList.cshtml)
 - Added null-values in User, Group and Event Type drop downs.
 - Added visuals for user lists and group lists. Need a change of the DB to implement further though.
Merge branch 'master-dev' of https://github.com/foxhide/PKSU-Gruppearbejde into master-dev