Updated requirements.txt
Optimized queries
Added Tournament.get_latest_round method
Added .boolean = True to boolean-returning methods to show them as BooleanFields in lists
Added permissions-restricting mixins
Added the rest of columns to Player list display
Fixed RefereeProfile change form
Added 'is_finished' column to the Tournament list display.
Replaced 'user.id' usage with 'user.pk' usage
Random bits of refactoring: changed package and module structure, moved some classes