Update 2.15 release notes to mention private changes feature

Add the initial description of the feature and entries in the REST API
section for the new endpoints.

Change-Id: I3dd87a60fc925004a07553e8b1581746151f3d9e
2 files changed
tree: c291d1361e0eb149808bb1925b4eb03649deba2d
  1. docs/
  2. images/
  3. releases/
  4. about.md
  5. COPYING
  6. index.md
  7. issues.md
  8. navbar.md
  9. README.md
README.md

Homepage for Gerrit Code Review.