Missing Message::staticId definition, fix casts.
Provide a default Service::onSet() -- only onRequest() is obligatory.

Some services will not implemet a onSet, so don't make it a pure
virtual.  Only onRequest is still pure virtual to make sure no one
instantiates Service.
By default create a Service Manager Service on each Sensorino.
Include the sender ServiceId in each PUBLISH, ERR.