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.
This adds a basic tutorial for getting started with tye.
There are a few gaps we need to follow on, specifically:
- Organization of documents
- Content of tye deploy instructions
- Any follow up tutorials