Allow all base images to be overridden using build arguments

[leochr]

Change Dockerfiles to allow the base image to be overridden by a build argument. This will allow the images to be built using a different base image (from a mirrored image registry or from staging registry before publishing)

[kabicin]

OL ci.docker PR: #573
WL ci.docker PR: WASdev/ci.docker#638