Fix SRB2 plugin. Now we can finally filter SRB2Kart!

There's no bad that comes with some good! The new server schema defines the kind of application the server is, so now we can finally get these pesky incompatible servers out of the list :D

The changes have been rather marginal and reasonable, good for the SRB2 team. I wish that I had a bit more time and get the gamemodes to function more properly, but I gotta go somewhere now.