REP-1148 Packaging Improvements

Most of this is work that @wdschei did on REP-853-valve-launcher. I dropped all of the work that was Servo specific, but I _think_ I got everything else. I did not pull over Bill's notes since some of them are no longer applicable. If desired, I can recreate those notes.

Note that I also kept the git-commit-id plugin and the properties-maven plugin. Together, these plugins make git information available to our pipeline. I believe the original intent was to use that information to tag snapshots with commit refs. We also provide a git.properties doc file on installation. This provides information on the exact build of Repose a user is running, but I'm not sure whether or not we should keep this.

I've probably opened this PR a bit early, but I'd like to get eyes on it as early as possible to help identify any issues.

EDIT: I pulled @wdschei's changes from #1147 (REP-1120) into this branch.