Merge branch 'stable-2.15'
* stable-2.15:
bazlets: Replace native.git_repository with skylark rule
Upgrade bazlets to latest stable-2.15 to build with 2.15.5 API
Upgrade bazlets to latest stable-2.14 to build with 2.14.15 API
Format all Bazel build files with buildifier
Migrate (i.e. move) `tools/bazel.rc` to `.bazelrc`
Update bazlets to build with current latest 2.14.14 API
Make plugin compile against stable-2.15
Add CSS styling to change message
Allow change message to be inherited from parent project
Change-Id: I150a9e696c708db4a79f79594726ba41546b3704