Create html template
Add translation
Add property for easy access to list of AK owners to AK model

Resolve first partial task of #7

place in event not required
track in AK not required
building and properties in room not required

add model class for availabilities
register availability model for admin view
add availability migration
add German translations for availability model
remove availability modelling TODOs

create AK Types
create AK Tracks
create AK Tags
create AK Requirements
create AKs