Draft of release notes for 10-7

@lamagnifica @mhoeber @explorerleslie Please review. (Leslie - in particular, can you review the bullets that have to do with discussions?) Built version at http://draft-107-release-notes.readthedocs.org/en/latest/10-07-2014.html.
This makes it sound like we are encouraging everyone to use this new feature. I'd rephrase somewhat to make it clear that *if* you choose to implement the feture, you complete its configuration before your course starts