Respect "use for snapshots" and "use for prereleases"

[isc-tleavitt]

Not sure if this is here, zpm, or both, but I suspect it's here.

If I disable "Use for Snapshots" and/or "Use for Prereleases" - e.g.:

zpm "repo -n registry -r -s 0 -pre 0"

Snapshot and prerelease versions are still listed (zpm "repo -list-modules") and installed (via zpm "install").

[daimor]

I'm pretty sure it was not implemented, at all, for the registry. And I think, best way to implement it, on both sides

[isc-tleavitt]

I'm hoping to carve out some more time this month for open source projects - can possibly contribute on both ends.