Add Teams

Add teams to game.
Teams are expressed as TeamStrings for each player, customizable in
the settings.ini file.
Players with identical TeamStrings are considered a team.
If one team is on board, its players all get the score.
Team members can also choose to be shielded by their own attacks and
pass through their own fences.
Fix Pickup bug

Fix bug where projectiles cannot be spawned as pickups.