Add Dockerfile.ci to speed up Jenkins.
Add Dockerfile.ci to speed up Jenkins.

alexharrington/xibo-cms,alexharrington/xibo-cms,xibosignage/xibo-cms,dasgarner/xibo-cms,alexharrington/xibo-cms,xibosignage/xibo-cms,dasgarner/xibo-cms,PeterMis/xibo-cms,xibosignage/xibo-cms,dasgarner/xibo-cms,dasgarner/xibo-cms,alexharrington/xibo-cms,PeterMis/xibo-cms,PeterMis/xibo-cms,PeterMis/xibo-cms,xibosignage/xibo-cms,alexharrington/xibo-cms,dasgarner/xibo-cms,xibosignage/xibo-cms,dasgarner/xibo-cms,xibosignage/xibo-cms,PeterMis/xibo-cms