BuildMojo - imageTags parameter added to tag an image with additional tags

This PR allows to apply additional tags to the image after it's built, using, for example, environment variables, such as build number.
This also applies to a default tag or any other tag set manually. I don't believe tagging instance should try to see if an identical tag already exists and reject the tagging operation if one is found. Tags in docker are not immutable and are frequently overwritten when an updated version is pushed. Arguing whether this is good or bad practice could be a different subject but so far that's this is the way it is, at least with Docker Hub.