Ban page pagination, cleanup/fixes

Backend
- SteamAPI constructer is now a classmethod
- Remove isbanned, make active ban querying smarter
- Added level to Matches
- util.py no longer imports database
- Fix some minor issues with the ban-list api handler
- Added match url stubs
- Make flask do type-limiting on some routes
Frontend
- Bans are now paginated, rendered in a simple/concise way
- Profile now shows if a user is banned (POC mostly)