builtin docker

[progrium]

* Optionally have commands come with their own Docker Engine instance. It would also be stateless, but allows you to perform Docker operations from your command, like builds and pushes, but also use or run programs in Docker for the duration of the command.
* Similar implementation to Envy, but stateless and per command
* Implementation notes
    * Needs to start before command
    * Needs to be cleaned up after command
    * Label with user and whatever else for resource reporting
    * Enabled for a command via some per command settings?
    * Which image to use? Something based on Alpine...