Define a project-template for horizon plugins
Define a project-template for horizon plugins

The horizon plugins all use a set of consistent jobs, but we're
currently copying them in. That means making coordinated updates
is a bit harder. Make a project-template that horizon plugins
can use.

Change-Id: I6ecba7d593268654535aa37ef6ae62baebb58378

openstack/horizon,NeCTAR-RC/horizon,NeCTAR-RC/horizon,ChameleonCloud/horizon,NeCTAR-RC/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,openstack/horizon,openstack/horizon,openstack/horizon,NeCTAR-RC/horizon