Add Github action for building a Docker image for testing

[gonuke]

This adds capabilities to use Github actions to build a docker image that we can then use for CI unit testing.

• builds the docker image only including dependencies
• uses that docker image to run tests
  • checks out the repo
  • saves Github secretes in the environment for the RLM server and RLM password
  • uses sed to update the license file with those secrets
  • runs pytests

[gonuke]

Making progress here - two of the tests work fine.

[gonuke]

Withdrawing this because @connoramoreno replicated it in #95