Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Add the standard LICENSE file
  Upgrade bazlets to latest stable-2.15 to build with 2.15.11 API
  LfsApiServlet: use LfsRequest.is(Upload|Download) methods

Change-Id: Ifc0fab109c0aacad3ed1cfc96fc153533c356f83