[FEATURE] Add Backend handling

* Modify tca of day, room and slot to make it easier to edit
* add resource handling
* Add backend module
* Add ajax handling for creating sessions
* Add ajax handling for updating sessions
* Add drag and drop moving sessions to grid and stash
* Make breaks not droppable

Resolves: #
Releases: 6.2
Change-Id: I1bd3991d0337d3be6c2c8d4b124401d2aaf3cb56
Reviewed-on: https://review.typo3.org/25139
Reviewed-by: Sebastian Fischer
Tested-by: Sebastian Fischer