Update rpc_api docs with example version update

Update the rpc api devref docs to include an example of what a change
that includes a minor version increment looks like.  I hope this will
help clarify for people what all is included in an API change that
requires a version bump.

Part of blueprint rpc-docs-and-namespaces.

Change-Id: I9c53d3518b200412701b19958d7cbf1ed03d643e
Merge "Update rpc_api docs with example version update"