Remove slow/dumb players from staff bots during network games

[otizonaizit]

When students start running network games to play against more serious opponents than the simple demo bots, they are currently playing against a random collection of older staff players. We should clean up that list, and only leve there those players which are fast enough and which are good enough to be better than the demos. We could also think about storing some of the best bots from the students from previous years.