Add unit restrictions to lobbies

[geekingfrog]

Similar to game options, but it's represented differently in the start script, so we need something at the proto level as well.

[Hectate]

I think I know how this is supposed to work, but want to make sure:
For each unit restriction the client wants, the key will be the unit name and the value will be a number representing the max number of those units? Set to zero and that unit is unavailable entirely for the match, right?

armflea: 0 will disable Armada Tick, for example.

[geekingfrog]

I think so? I'm just following the format from the autohost/start schema