Feature Request: Designate build containers for images

[srobertson]

To avoid building images containing build tools, it would be nice to designate that an image is built using another image.

For instance I might create an image that has build-essentials in it from debian/ubuntu and call it sixsense/builder_bob. This image doesn't have to be built by shipwright but it could be.

Then I'd modify .shipwright.json to designate that an image is built inside builder bob like this.

{
  "version": 2.0,

  "namespace": "sixsense",
  "names": {
    "/": {
        "name": "sixsense/buildme",
        "build_with": "sixsense/builder_bob"
     }
   },
  ...
}

Another option is to introduce our own Keyword to the Dockerfile

Examples of this can be seen here.
http://neophob.com/2k014/08/inception-a-docker-image-that-build-docker-images/