* Cleaned up Docker documentation and process
* Added back `build` section to Dockerfile so we don't have to
manually build it separately, simplifying the quick-start process
* Added a healthcheck to make it easier to see when the container
was done initializing. Currently a little ugly since it has to
check both URLs for liveness
* Removed CONDA_FORCE_UPDATE from env file since we don't user conda
anymore
Note - `build_docker.sh` is seemingly obsolete but I left it for now
with a comment in case it's ingrained in somebody else's workflow.
* Minor readme fixes
