Proto:
- Minor corrections in context.proto

Common:
- Minor corrections in common.orm.backend
- Improved definition of orm.Model class with get_instances and get_references
- Extended ORM unitary tests with get_instances and get_references

Context:
- Implemented missing methods in ContextClient
- Started to implement new Context data models using ORM.
- ContextModel functional using ORM and gRPC.
- Arranged old code file placing

- Context Database API and ORM rework in progress

- Complete rework of Database API
- Integration of Database API into Context
- Improvement of API

This commit is not a final implementation, just an intermediate backup.

Fix renaming of compute.proto methods from snake-case to camel-case. Added minor naming improvements.

Common:
- minor bug resolutions in Context API

Service:
- first functional version of Service (implementation of GetConnectionList postponed)
- minor corrections in service.proto and related files
- implemented unitary tests

Common:
- Improvements in Database API definition and unit tests
- Implemented additional Assertions to be used by unitary tests

Context and Device:
- Improved logging of errors.

Service:
- Implemented service methods (except GetConnectionList). All methods are under active debug.
- Partially implemented unitary tests

General changes:
- implemented data type checker class
- improved database Entity/Collection/Attributes API
- implemented grpc message parsing assertions
- integrated code coverage analyzer and reporter with code testers
- added example topology NSFNET

Common to device & context services:
- improved database context API and its tests

Context service:
- updated context proto file: added AddLink/DeleteLink RPCs, added LinkId to Link
- minor changes

Device service:
- implemented device service functionality
- improved device client
- updated genproto script
- updated device proto file: configure request becomes a Device message
- updated context proto file: operational status: added KEEP_STATUS, changed DISABLED
- moved device tests to global scripts
- extended unitary tests
- temporarily disabled integration tests