refactor(policy): add validation at PolicyRuleDevice

See merge request teraflow-h2020/controller!161

refactor(policy): add validation at PolicyRuleService

See merge request teraflow-h2020/controller!160

refactor(policy): add validation at PolicyRuleCondition

See merge request teraflow-h2020/controller!159

- fixed parsing of custom rules in unitary tests

- Added missing log dump in unitary test

Common and Context changes:

See merge request teraflow-h2020/controller!157

- added exposition of redis-tests service for testing with Redis backend
- moved delete logic from Context Servicer to ORM components
- added support for constraints of different kinds

fix(policy): update ConstraintIsolationLevel object

See merge request teraflow-h2020/controller!158

refactor(policy): implement builder pattern for EndPoint

See merge request teraflow-h2020/controller!152

Automation/implement builder pattern for end point

See merge request teraflow-h2020/controller!151

- added helper methods to copy/update grpc messages: config_rules, constraints, endpoint_ids, service_ids
-  extended Context ConstraintModel to support different types of constraints
- extended EndpointModel with get_endpoint helper method
- extended SliceModel to incorporate config rules

Extended Context proto files with slice config rules, endpoint priority constraint, and modified isolation level constraint

See merge request teraflow-h2020/controller!156

- Slice: added config rules
- Added EndpointPriority constraint
- Modified IsolationLevel constraint to contain a repetition of items

Arranged deploy scripts

See merge request teraflow-h2020/controller!155

- corrected service name computation in expose_ingress_grpc.sh script
- corrected log format in deploy.sh script
- added control to configure Grafana only when both webui and monitoring are deployed

Added tutorial for debugging with VSCode

See merge request teraflow-h2020/controller!150

- added sections describing installation of Python Extension in VSCode
- added section describing how to export and test connectivity to services through gRPC

refactor(policy): change proto files names

See merge request teraflow-h2020/controller!154

refactor(automation): modify automation.proto to use context.Empty

See merge request teraflow-h2020/controller!153

Draft of tutorial to configure environment and VSCode to debug individual TFS components

refactor(policy): refactor PolicyService & PolicyGateway interfaces

See merge request teraflow-h2020/controller!149