Merge pull request #44 from adriaanm/master

Maven-based PR validation scripts
Build docs during pr-scala-test.

TODO: split into parallel jobs

Will still need to build pack first,
then pass it to test.pos_neg | test.run | docs
Fallback for older PRs

once all PRs are based on top of #3109/#3108, this can be reverted
fixup! a95c1ce55a