Option to select target DF version

[PeridexisErrant]

Currently, the tool just collects the latest version of everything. This works very well in the long stable periods before a major DF release, but not so well when things are changing rapidly and (eg) a new DFHack version may target a previous DF release.

It would be nice to have an interface to specify which DF version should be used, rather than hand-editing _cache.yml (this works, but it's a real hack). For bonus points, this could auto-detect the target based on DFHack version, and collect older releases of graphics packs etc from github.

Status: wishlist, but unlikely to be implemented. There's no way to automate this and guarantee a coherent pack, so I prefer to force doing it by hand.

[PeridexisErrant]

Done in recent commits, eg ec5e7b3. config.yml now allows you to specify whether to use the latest DF version, or that compatible with the latest DFHack. Either way, incompatible contents - DFHack, Therapist, and components which require DFHack - are omitted as appropriate; this means that an automatic nightly pack should always (mostly) work.

Downloading older versions of components is off the table, as there's no reliable way to do it safely in the general case.