availabilities in AK submission
availabilities in AK wish submission

Closes #74

Introduce new mixin
Replace edit & create views by redirects to overview page
Prevent inserting/updating for AKs and Owners
Disable interest counter
Hide interest button
Update translations

Hide wall (hide button in plan, redirect when calling directly)
Show message on normal plan & hide current and next AKs
Link only a single schedule view in Dashboard but not current AKs and wall
Update translations

adjust other buttons
re-generate translations

Add new helper property to model
Add and use template tag for color coding
Add helpfer functions for color blending (gradient and simple)
Also show timestamp of last edit in admin view
Introduce setting to control which changes will be higlighted

Move encoding to own files that can be included
Add url for linking to detail page to event encoding
Add color coding for category and track to event encoding
Introduce room hierarchy (building + room)

Introduce common base template for plan views
Move breadcrumbs to own file for easy referencing
Load common fullcalendar base files in base template
Introduce new block for other fullcalendar operations

Adapt filenames, references and URLs
Adapt settings keys
Adapt translations
Fix wrong settings keys in wall view

Add views
Add templates
Add urls
Add translations
Add three corresponding settings to central settings file
Minor: Fix typo in plan_akslot