Merge branch 'stable-3.1' into stable-3.2

* stable-3.1:
  Bump plugin API to 3.1.15
  Bump plugin API to 3.0.16
  Bump plugin API to 2.16.27
  Convert UI filters to links and display always

Change-Id: I02687957853387c038a3b62c6fe3a38bf8190174