Merge branch 'stable-2.15'

* stable-2.15:
  Fix common-dbcp dependency name for in-tree build
  Format BUILD files with buildifier
  Format Java files with google-java-format 1.6
  Update bazlets to latest revision on stable-2.15 to use 2.15.2 API
  Bazel: Switch to using release plugin API
  Adapt to recent API changes

Change-Id: Icbf8533f0c0ac397852585b439630663f8a79ab7