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.
That's not quite correct. (Warning: Possible pedantry ahead.) Some of the flush left items are general topics, and those are set on the **Advanced Settings** page. However, the names of other flush left items are set at the component level and don't necessarily correspond to section, subsection, or unit names. In a Discussion component, the course team fills in both a "Topic" and a "Subtopic" setting. The text in the "Topic" field corresponds to the flush left text; the text in the "Subtopic" field is the indented text. (See https://edge.edx.org/courses/sylviaX/TEST10/2014_T3/discussion/forum - "Week 1: Getting to Know You" in the list of all topics doesn't correspond to any section, subsection, or unit headings; it's set in the **Topic** field of a Discussion component.) 

Additionally, from a viewing standpoint, it's possible to click a flush left topic (**Topic** field in Discussion component UI) that has indented topics under it (**Subtopic** field in Discussion component UI) and see the discussions for all the subtopics in that topic. Try clicking **Week 2: Homework 1** in the test course; you'll see 5 topics. If you go back to the list and click **Ionian Mode** under **Week 2: Homework 1** you'll see 2 topics; if you click **Dorian Mode** you'll see 3.

You're right that those distinctions don't matter much here, though, since when the user creates a new post he can only select from general course discussions and subtopic names. But I'd rather keep using both "topic" and "subtopic" for consistency.