Slightly change formatting
Use flask-classy, move UsersView to a separate file
Move non-db parts from db/ to core/
Move code from db/flask to __init__

This way, we don't have to remember to import db.flask everywhere we need
Base.query.
Change templates
Merge branch 'classy'

* classy:
  Change templates
  Move code from db/flask to __init__
  Use flask-classy, move UsersView to a separate file