Adds support for GAGS underwear / uses it to make digi lizards look less bad

[MrMelbert]

1. Underwear can now have a GAGS config set, in the future this allows for more complex underwear sprites. For instance, rather than having the British and American boxers, we can let people make any country boxers.
2. Uses this to generate digi sprites, much like we do for jumpsuits

Look at this goblin