Prepare for 4.12.0 release
Prepare for 4.12.0 release

Set plugin version to 4.12.0

MarkEWaite/git-plugin,jenkinsci/git-plugin,jenkinsci/git-plugin,jenkinsci/git-plugin,MarkEWaite/git-plugin,jenkinsci/git-plugin,MarkEWaite/git-plugin,MarkEWaite/git-plugin