- progress on migration to CockroachDB (partial)

- reviewing integration with CockroachDB
- reviewing context REST API
- reviewing database schema
- reviewing code

Context:
- ORM models completed and tested
- Deactivated unneeded code-linting warnings
- Improved coding of fast_hasher method
- Added test unit for fast_hasher method
- Improved organization and structure of test units

Context:
- Moved old code to separate folder (will be removed in future commit when development is completed)
- Solved bug with Link-EndPoint retrieval
- Implemented ServiceModel and related unit tests
- Moved helper methods to Tools.py file in database

Common:
- added ORM helper function get_related_instances
- minor modifications in ORM framework

Proto:
- field/message/enum renamings in context.proto to normalize notation

Context:
- Expanded service/database/Models.py into separate models to facilitate coding
- Completed implementation of Get/Set/List/Remove methods for Context, Topology, Device, Link, and EndPoint; also completed for relation models between topology and device/link, and ConfigModels
- Implemented test units for Get/Set/List/Remove methods for Context, Topology, Device, Link, and EndPoint
- Implemented skeleton for Get/Set/List/Remove methods for Service.
- Added Tools.py with helper methods to fimplify handling of enums between ORM and gRPC messages.