Issue #120 Add support for --tag to lift, provision and push

Sorry about all the back and forth this evening. Git and I had a falling out

This Pull Request should be everything we need.
If there's no ':' then the split just returns the full string in `imageParts[0]`.

There would be problems if someone was using a `:` for anything other than a delimiter between an image name and a tag, but then they would be going against Docker convention anyway so would have problems elsewhere too.