Implements two flavor of library support for service-discovery:
- GetConnectionString (arbitrary strings) augmenting existing
functionality already in asp.net core
- GetServiceUri (uris) can be combined
from a protocol/host/port triple
See the **extensive** doc `service_discovery.md` that is filled out in this PR. That documents pretty much everything about how this works now.
* Add test for container -> host communication.
* Small tweaks
- Modify frontend-backend app to print backend url
- Fix log in docker runner
- Rename test to use docker instead of container
* More clean up
- Don't set container port if the service isn't a container
* Bind to all interfaces on linux only
- Turns out the same alias works fine and docker will
associate multiple IPs with a single alias
- Remove the docker run command from the output and leave it in the log
- Dump out the backend host names in the frontend backend example