Merge branch 'stable-2.15'

* stable-2.15:
  Automatically format BUILD file with buildifier lint mode
  Upgrade bazlets to latest stable-2.15 to build with 2.15.9 API
  Upgrade bazlets to latest stable-2.15 to build with 2.15.8 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.18 API
  Bazel: Include eclipse-out directory in .bazelignore
  Add explanatory comment to empty BUILD file(s)

Change-Id: Ib1bc00a5c68de7b98fcb9676de5580cb6bc9c048