Determine location for building kernel images and allow use via Enterprise Gateway

[kevin-bates]

The container-based kernel providers (KubernetesKernelProvider, DockerKernelProvider and DockerSwarmKernelProvider) require the use of docker images for supported kernels. This repository has everything needed to build those images, so, from that standpoint, it makes sense to host the image builds.

It would also be good to allow these images to be used from Enterprise Gateway as well. This implies that version information in the scala jar filenames should be referenced in non-specific manner, since the toree-launcher jar built from EG will reference the EG version, while the same jar file built from this repo will reference the RKP version.

We should also ensure there are no dependencies on repository-specific behaviors, etc.