Solve minor issue in unitary test of Context that prevented tests to finish correctly in random cases.

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

- Implement WIM REST API for OSM
- Implement IETFL2VPN REST API
- Implement unitary tests for OSM-Compute-Service workflow

First functional version of Service with Service Handler for L3NM-Emulated services using Emulated Devices

Updated gRPC proto files to prevent trouble with KPI sample types in devices, also updated files related to this issue.