Rethink current usage of docker

At the moment clickable will try to start docker and add the current user to the docker group, without asking, except for the root password. I don't think this is a good idea.

One reason is that the ability to create docker containers is root equivalent.

Another is that some people want to run docker commands as root. Or another user. Or they want to use a non-standard docker socket. Or they use docker-machine.