Feat/events basics

[JohanHjelsethStorstad]

THIS PR SHOULD BE MERGED AFTER #313.

This PR adds the basics of the event system, including event-models and the main event pages. Next up:

• Event tags (can be started now)
• Registrations (Needs money to a degree)
• event-auth (needs visibility)
• event migrations (can to a degree be written now)

[JohanHjelsethStorstad]

And no this PR is not 91 commits. Many of them come from #313 (not merged yet)