Killed old C++ filter code, added Game.ShouldConnect
- Gutted out network filter code in favor of controlling incoming connections in C#.
- Commands removed: `banid, banip, removeip, writeid, writeip, listip, removeip, sv_filterban, sv_banid_enabled, sv_banid_dev_enabled, sv_logbans` - probably a few more too.
- Added `bool Game.ShouldConnect( long playerId )` - returning false here will reject the incoming connection before the client entity is created.