Add embeddable-build-status-plugin support

This is a 1st pass.

Also weird it looks like my fork brought in the original ```https://github.com/mocleiri/github-oauth-plugin``` repo instead of the JenkinsCI org one.

I'll fix that when I get back to this. To tired to do it now.

Issue: https://issues.jenkins-ci.org/browse/JENKINS-25809