[EPIC] Streamline/simplify our docker compose

[jchartrand]

The docker compose for the dashboard and related services is a bit clunky and has some things that aren't needed - like the custom network, and the import of the secondary compose file.

Could also look at moving all environment variables from .env files directly into the docker compose for easier evaluation by prospective deployers. They can be easily moved back out to .env files for production deployments.

• Reconfigure admin dashboard's message queue initialization #43
• Enable production build (specifically for admin dashboard) #44
• Add multistage builds to docker files #45
• Optimize image layer caching #46
• Squash image layers for final docker hub image build #47
• Optimize docker ignore  #48
• Add HEALTHCHECKS docker function #49

[alexfigtree]

Kerri asks where/how this can all get documented, in README, etc.