VSS signal representation

On 2021-03-29 RPC call there is an interest to shorter version of a signal than its full path.

One idea @magnusfeuer proposed was typedef for shortname alias. As there will be a curated catalog of services we could impose conventions for doing so. I wondered about a namespace prefix and final node name, less the path/branch information.

If a given service has concept of speed, we only care it came from VSS and do not care which (GPS, engine) speed was chosen. We want to avoid proliferation of aliases, eg velocity being introduced.