Morph-kgc

This release of Morph-KGC features `RML views` over tabular sources. RML views empower the mapping of tabular data to RDF enabling complex joins, transformation functions or mixed content by using SQL, a query language familiar to data engineers.

Changes
94: Parallelized materialization when running as a library on Linux.
89: Support for [schema-qualified names](https://www.w3.org/TR/r2rml/#dfn-schema-qualified-name).
87: Compacting and simplifying the internal representation of quoted maps.
86: Emty arrays in JSON are now processed correctly.
81: CSVs with any separator.
80: Support for `.rml`, `.r2rml` and `.rml-star` file extensions.
76: Support of mapping rules with all term maps being constant-valued.
65: Handling non-atomic write operation in Windows.
93: RML tabular views.
84: Compacting and simplifying the internal representation of subject, predicate, object and graph maps.

Support of [Natural mapping of SQL values](https://www.w3.org/TR/r2rml/#natural-mapping)

- 67: [Natural mapping of SQL values](https://www.w3.org/TR/r2rml/#natural-mapping)
- 67: Integers generated without .0

Solving 62.

- Support for attributes in XPath.
- Support for remote JSON and XML files.
- Support for remote mapping files.

Minor performance enhancements.

This major release features **[RML-star](https://kg-construct.github.io/rml-star-spec/)**.
- Support for [RML-star](https://kg-construct.github.io/rml-star-spec/).
- Integration with [Oxigraph](https://oxigraph.org/pyoxigraph/stable/index.html) via `materialize_oxigraph`.
- _XPath 2.0_ has been replaced by _XPath 3.0_.
- `clean_output_dir` has been removed as a parameter in the config file. Now Morph-KGC truncates only RDF output files by default.
- It is now possible to generate multiple (smaller) output RDF files using `output_dir`.
- RML-star test cases added to continuous integration.
- New documentation replacing the Wiki.