Add release notes for Djblets 0.9.3.

Review Request #8123 — Created April 13, 2016 and submitted — Latest diff uploaded

Information

Djblets
release-0.9.x
46b2552...

Reviewers

This covers the improvements made to the extensions framework for
includes and default bundles, fixes for metadata processing, webapi
logging additions, and fixes to the config forms.

Built the docs and read through them.