- Added definition of algorithm in proto file
- Minor code comments and TODOs added

- 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.

- initial skeleton (not functional)

Policy component's protobufs are updated based upon
the Event Condition Action (ECA) model.
Minor fixes are applied to the slice.proto in order
to compile.

Signed-off-by: Georgios Katsikas <katsikas.gp@gmail.com>