Reasoner-validator

- Added (optional) OpenTelemetry functionality for web service.

- demoted **dangling nodes** 'error' down to 'warning' message, annotated with the list of missing nodes as the identifier

- Upgrade to Biolink Model Toolkit 1.1.2
- Removed all residual references to 'sanitize_trapi_response()' (warning: validation with pre-release versions of TRAPI 1.4 earlier than 1.4.2 may trigger some funny false positive validation messages)
- BiolinkValidator.PREDICATE_INCLUSIONS added (just with "biolink:interacts_with") to bypass 'mixin' Biolink Model validation error (pending full community review of the 'mixin' status of this predicate); unit tests modified to suit
- plus a small internal DRY refactor in test suit with respect to LATEST_BIOLINK_MODEL_VERSION

- Detect missing knowledge_graph names (resolves part of issue35)
- detection of uninformative QNodes (resolve issue14)
- Dangling ("unused") nodes detection is fully implemented (complements "edge nodes not in nodes list" detection already in place); resolves issue74

- 'attribute_type_id' term which are Biolink (node) 'category' or (edge) 'predicate' terms generate a specific warning (not just a 'not an association slot' warning)
- Knowledge graph edge qualifiers qualifier "value unresolved" validation error demoted to a warning

- glitch while publishing to pypi.org