Add course author notes for 7/16 release

@mhoeber @lamagnifica Please review. Draft at http://draft-release-notes-7-16.readthedocs.org/en/latest/07-16-2014.html.

I didn't include the following; let me know if I should:

- https://github.com/edx/edx-platform/pull/4095 (creates an Open edX footer)

- https://github.com/edx/edx-platform/pull/4172 (e-commerce enhancements - I don't think these are externally visible yet)

- https://github.com/edx/edx-platform/pull/4353 and https://github.com/edx/edx-platform/pull/4368 (these two are specific to annotations, which I think only Harvard uses and we don't want to publicize)
agreed but this sounds like it's written for students.  maybe recast to something like "course authors can configure ora so that student s can . . .

makes me think we should start reorganizing release notes the way we do for newsletters -- organize by "For Course Staff" and "For Students" instead of base on our products.  will try next week.