Rdflib 6.0 and json-ld fixes

[ashleysommer]

Fixes #45
Replaces #46

Changes:

• Bump min rdflib to v5.0.0
• Remove json-ld from requirements
  • OWL-RL imports rdflib_jsonld in a try: except wrapper anyway. Its an optional feature
• Detect if RDFLib 6.0+ is in use, if so set json_ld_available=True without importing the module.

[ashleysommer]

@nicholascar
Can you please review and merge, though I'm not sure how to correctly put out a new OWL-RL release.

[nicholascar]

Can you please review and merge...

Sure, will do a bunch of rdflib reviews tonight.

...though I'm not sure how to correctly put out a new OWL-RL release.

I've got access to OWL-RL on GitHub & PiPY, so I should be able to put updates through.

[Panaetius]

Thanks for this, this is a better solution than the one in #46, I'll close that PR in favor of this one.

[nicholascar]

version tagged, readthedocs updated and PyPI version released: 5.2.2

[ashleysommer]

Thanks Nick!
As a direct result of this:

• PySHACL v0.16.2 released
  • works with rdflib 5.0.0 or 6.0.0, works on python 3.6 or greater, works with built-in rdflib_jsonld or imported.
  • Last version of pyshacl to work on rdflib 5, and last version to work on python 3.6
  • https://github.com/RDFLib/pySHACL/releases/tag/v0.16.2
• PySHACL v0.17.0 released
  • works only with rdflib 6.0.0 and above, works only with 3.7 and above, works only with built-in rdflib_jsonld.
  • https://github.com/RDFLib/pySHACL/releases/tag/v0.17.0