Custom asteroids data packages

I've added support for installation of mod-specific data files for Custom Asteroids. Compatibility files for e.g. RSS or Alternis Kerbol will need to be provided separately. How does relationship resolution work if, for example, a player has RSS but nobody has uploaded any Custom Asteroids data files for it? Will CKAN say "There's no `CustomAsteroids-Pops` that I can install, therefore I can't install Custom Asteroids"?

@pjf, as noted in the JSON comments, I've got a bit of a problem with RSS compatibility. The data files are not compatible with the default RSS settings, but they *are* compatible if the player's installed an optional config that uses a rescaled Kerbol system instead of the solar system. I'm not sure how to indicate that this is an exception to the overall lack of compatibility.