A new code runner api: docker-run

Docker-run provides a http api for running code inside transient docker containers. The communication with the docker daemon happens via it's api over a unix socket and is meant to run on the same machine as the docker daemon.

This could be used as a drop-in replacement for the old glot-run if used together with the new glot-run 2.

It is written in Rust and should be a lot easier to set up and configure than glot-run. It also has a lot better error handling and reporting.

Docker-run has been used in production on glot.io since November.