Reasoner-validator

- Removed `check_trapi_validity()` standalone API method to enforce a two-step process of instantiating a `TRAPISchemaValidator` instance then calling its `is_valid_trapi_query()` method.
- Spurious leading newline removed from TRAPI and Biolink Model validation version reporting log messages
- Fixed insidious edge source validation message reporting bug which masked all but the first of edges with a specified validation error
- Minor tweak to validation codes definitions to reduce duplication in reporting output or clarity of definition
- Fixed (and extended some) unit test cases related to all of the above.

- Generally repaired validation 'sources' ('source_trail') context recording to cover all applicable validation message cases (especially, edge 'qualifier' validation); tested with unit tests
- TRAPIGraphType class moved up the class/module hierarchy, alongside ValidatorReporter; strict_validation as Optional[bool] wrapped in the is_strict_validation() method which uses graph_type to decide on None default strictness (based on graph type)
- TRAPI and Biolink Model versions resolved now only reported in logger.info, not stderr
- only preset target_provenance in validator reporter constructors, not the various method signatures
- add 'categories' into edge context labels for reports (long lists of categories may be challenging here but ...)

- Internal class hierarchy restructured for logical clarity in recent releases, formally highlighted in this release
- Most visible TRAPIResponseValidator class (previously) moved from the **`reasoner_validator.__init__.py`** package module, into its own **`reasoner_validator.validator`** module
- Some documentation repair

- TRAPI qualifier validation enhanced by use of biolink:Association subclass slot_usage driven constraints (leveraging novel Biolink Model Toolkit 1.1.1 methods)
- Validation made TRAPI Response (TRAPI) **`schema_version`** and **`biolink_version`** aware, taking precedence over default (non-overridden) values of these version parameters.

- Added TRAPI Response schema version and biolink version validation warning codes
- Warning about 'biolink:BiologicalCategory' and 'biolink:InformationContentEntity' are not issued if these categories are parent categories of concrete category instances specified in the 'categories' list

- resolves reasoner-validator issue 89 by validating semicolon delimited strings of infores