Release notes 12-9

@mhoeber @lamagnifica @catong Please review.

@clintonb Since you're release lord (should that be capitalized?) this week, you get a sneak peek at the release notes. You don't have to do a thorough review, but feel free to read through them and let me know if anything seems amiss.
yes.
unfortunately, I am stuck in the midst of a git squash attempt gone wrong, and I can't switch to the branch that will have that change in it so that I can provide the reference to you. If I get a chance between meetings later today, and my git issue gets resolved, I'll try again. If not, see the edx-analytics-dashboard repo, ahodges/DOC1039 branch