- Correct attribute name component to components in Device message

- Added/Updated headers
- Added script to update copyright headers

- corrected gRPC format of Events in MockMessageBroker

- added missing log messages in MockContext

- corrected SetContext
- corrected SetSlice/RemoveSlice
- implemented GetSliceEvents
- corrected RemoveService

- Arranged .gitignore & .gitkeep files in common proto folder
- Created specific run_tests_locally script for Context component
- Moved imports from *.proto folder to common.proto folder
- Adapted common.tools.object_factory to new proto definitions for ConfigRule and Constraint
- Extended common.tools.type_checkers to new proto definitions for ConfigRule and Constraint
- Removed context's genproto.sh script
- Adapted Events generated to new timestamp data type
- Minor code and linting fixing

- 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.

Common:
- added chk_attribute to type_checkers module.
- recovered run_tests_locally.sh

Compute:
- updated requirements.in
- updated Config.py
- updated RestServer
- implemented IETF-L2VPN NBI plugin
- implemented unitary tests for IETF-L2VPN NBI plugin including a Mock OSM client, and Mock Context and Service components