Permissions update

Old access level mechanism was not very elegant. This replaces how permissions are handled with a more extensible method of handling permissions. Also provides a method to manually assign someone permissions without worrying about house positions.

Database changes:
- New table `office_permissions`
- New table `user_permissions`
- Will remove `access_level` from `offices`
Every page that doesn't need a custom permission checking method should just be using `login_required(permission)` to require that a user has some permission to access a page.