Rework doc examples to run on localhost

At present, most DS doc examples use FQDNs. This probably arose because:

1. The best practice for setting up replication for real is to use FQDNs.
2. Sometimes FQDNs help you understand the instance, e.g. rs.example.com vs. ds-only.example.com vs. proxy.example.com.
3. Server IDs weren't strings and were useless to distinguish one instance from another.

This is annoying in practice. Either you fake FQDNs in /etc/hosts just to use the examples as is, or you edit every example after copying and before pasting. The Getting Started guide drops FQDNs in favor of localhost for that reason.

Assuming our readers are not limited to internal FR developers who use DS all day long, and assuming the common case when reading the docs is trying something out in dev on one's laptop, it would be good to favor usability by using localhost as the default, and distinguish by port numbers, comments in the examples, and server IDs where possible.