Ability to have multiple challenge.yml files in a challenge repo

[ColdHeat]

It could be useful to have multiple challenges specified in a challenge repo instead of just a single challenge.yml. Or perhaps having multiple challenges inside of a single challenge.yml file. Not sure what the right way to fix this would be.

[ColdHeat]

I think this problem is deeper than what simple fixes like --yaml-path can do.

I think we need to revamp the .ctf/config format entirely so that it has extra options in addition to the repo.