Add additional routes/query parameters for common queries on orgs/nodes/identities

[awrichar]

In the wake of #549, identities (including orgs and nodes) have become much more flexible and powerful - but fetching identities, verifiers, and DIDs can require multiple lookups.

Some suggested enhancements to reduce API calls in a few spots:

• /network/nodes/{nid} and /network/organizations/{oid} could be id-or-name lookups
• The above could possibly be extended to /namespaces/{ns}/identities/{iid} as well, but identities of different types could technically have overlapping names
• Lots of the "network" and "identities" routes could include a fetchverifiers bool in order to bring in an array of verifiers for each identity
• New route to look up a DID from a DID-ID such as did:firefly:org/org_1