Make a docker image for using Plasma

[PaulBone]

We already have a docker image for developing Plasma, Split it into two, a base image for both to inherit (or copy from) and make a new image that includes an installed version of Plasma. Then we should end up with three images.

• Base image (other two images use this, humans don't)
• Plasma dev image (people may use this image to contribute to Plasma)
• Plasma image (people may use this image to try Plasma)

[PaulBone]

Also we should make Plasma source tarballs and binary packages. Docker is just one option for binary packages.

[PaulBone]

I want to get automated builds in CI first #431

[PaulBone]

Part of this should be to make the image provide the plasma tools, but the editor sits outside that, so the docker container should have a view to the git repository outside it's container. This should be done for both the docker containers, for either developing plasma or for using it.