Support multiple 'generic packs'

[ChipWolf]

This would be useful for stacking together common packs across all of our servers, then more specialised packs for regional/individual servers.

I expect this would work exactly the same as the current system, just processing each pack sequentially.

[itzg]

Good idea and yes quite doable.

[itzg]

You would want any jars that weren't present in the zips to be removed from the destination mods/plugins directory, right?

[itzg]

You would want any jars that weren't present in the zips to be removed from the destination mods/plugins directory, right?

nm, looking at the code I realized the manifest tracking takes care of cleaning up iterations of packs.

[itzg]

The pushed images now includes support for GENERIC_PACKS

https://github.com/itzg/docker-minecraft-server/#generic-pack-file