better display of StundenZuteilung in admin
Processing of stundenplan edits changed. this should take care of github issues #13. Also speeds up the get processing quite a bit

Root cause of the bug was, however, most likely multiple presences of StundenZuteilungen for same Zuteilung. this is a serious bug if it still persist, should write some error checking code for database integrity here.
In Aufgaben Editieren, editieren link move to the left.
starting to use 1.7 migrations
Added zustimmungsDate Field
Forced Zustimmung at initial login of a user. Encoded via the is_active flag