Cleanup to idTech2 surface inspector.
Use executables path for launching engine. This is defaulted to engine path for most games, but adjusted for those which have their binaries in a different directory (e.g. Quake2World).
Setup engine, enginepath, executablespath and prefix more thoroughly for q2w.game.
Re-introduce 'quake2' flag is 'idTech2' flag for properly launching legacy games.
Merge pull request #238 from jdolan/master

Restore quake2 game description flag as idTech2 flag, fix launching legacy games.