Change the mods and modListFile argument handling a bit. Other tweakers will get a chance at looking
at them now - they're only removed right before launch.
Two new features. ModLists can have a "parent" mod list. Circularity will
result in a crash, so be careful. Mods specified in a child will override
ones from a parent (using the maven group:name:classifier triple to identify -
ignoring the version component)

Finally, ModSide is now doable in MANIFEST.MF. If you have this, it can tell
a mod to only load on a client, or on a dedicated server (though I'd watch out
before using the dediserver one, you'll never load in integrated servers then).
The default value is BOTH, which means you'll load both sides, other values are
CLIENT and SERVER, obviously. Perhaps, also, CAULDRON might be possible?