No quitters option on table creation

We can add such an optipn to restrict participants. Those who are fine with quits, or new users, can still play without setting that option.

Here is my initial idea whitch is to offer two levels:
- Default: you need to have finished at least one game (a match or a tourney, depending on what the table is for), and your quits needs to be no more than 20% of the matches played.
- Strict: same as the default, but 10% instead of 20%.

Alternativey we can check the non-quitting streak, though it's easily affected by accidental quits.