Bump starr to M7, along with module versions.

Allow extra-repo to make it easier to test e.g.,
a staged scalacheck while releasing modules.

TODO: replace desired.sha1's with jars for M7 starr so it's consistent
alternatively, we could just remove them -- no intention of allowing unreleased starr again

what say you, @gkossakowski, @retronym, @jamesiry et al?