Merge branch 'stable-2.16'

* stable-2.16:
  Add LICENSE(Apache V2) to go-import plugin
  Upgrade bazlets to latest stable-2.16 to build with 2.16.2 API
  Upgrade bazlets to latest stable-2.16 to build with 2.16.1 API
  Bazel: Include eclipse-out directory in .bazelignore
  Add explanatory comment to empty BUILD file(s)
  Update mockito to 2.23.4
  Upgrade bazlets to latest stable-2.16 to build with 2.16 API

Change-Id: I8c621268622179528fd1048bbb67f5f3c87a39f0