PathComp component:

- extended proto file to support retrieval of both services and connections, e.g., services requested + sub-services, and the connections and sub-connections supporting the services and sub-services.
- minor bug fixings in MockServicerImpl_Context and implementation of support for Slices
- implemented and pre-tested unitary tests for PathComp
- implemented in PathComp service the logic to retrieve context data, and the skeleton to retrieve the replies to compute requests.