hdt-rs: A Rust library for the Header Dictionary Triples binary RDF compression format

• SPARQL support by @GregHanson in https://github.com/KonradHoeffner/hdt/pull/66 (experimental "sparql" feature, API may change)
• HDT can now be written and can be converted from N-Triples by @GregHanson in https://github.com/KonradHoeffner/hdt/pull/60 and https://github.com/KonradHoeffner/hdt/pull/71
• improved error handling in https://github.com/KonradHoeffner/hdt/pull/61
• refactor HdtGraph into a trait implementation in https://github.com/KonradHoeffner/hdt/pull/78

Note that SPARQL is not the primary focus of the HDT file format. We have neither benchmarked nor optimized the SPARQL performance yet and even if that happens later it is still unsure how performant it will be. Most w3c tests are validated by an automatic test suite by @GregHanson using a git submodule but graphs are not supported. The command line application (CLI) for conversion and more is moved to 0.5.0.

Other changes include:

• Additional public fields by @GregHanson in https://github.com/KonradHoeffner/hdt/pull/54 (though this may be scaled back as have less need for it now)
• fix: dictionary needs to be able to save when there are no entries in the shared section by @GregHanson in https://github.com/KonradHoeffner/hdt/pull/58
• increase minimum supported Rust version to 1.87
• remove unnecessary 'langtag' and 'iref' dependencies

Planned for next release 0.5.0:

• a command line application (CLI) to convert to and from HDT and other RDF serializations and more
• ergonomic improvements to the SPARQL API
• potentially a SPARQL endpoint and HTML interface

Full Changelog: https://github.com/KonradHoeffner/hdt/compare/0.3.0...0.4.0