Resolve first partial task of #7

Basic design

See merge request !1

After this commit, only the top level static files folder is ignored, while apps may contain static files that can then be collected by django

Add suitable libraries to requirements
Load these apps and adapt their basic settings

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

add static root to settings, ignore static folder in .gitignore
add production deployment requirements to README
add production deployment instructions to README
change port in uwsgi config file

document project and (future) app structure in top-level README

add list of past contributors and current maintainers
add guideline for contributors

add settings_production to override certain development settings
add settings_secrets.py.sample to illustrate usage of production secrets

add Utils directory
add Utils README
add setup script
add check script
add update script
document usages in top-level README