set default jsonld version to 1.1. autoformat for corresponding files.

[WhiteGobo]

jsonld version 1.1 seems to be needed as standard in some cases, see issue #2606
This change might raise some mypy warning because version parameter in jsonld.parse now annotated with float. During runtime this change shouldnt change any behaviour outside from the default version.
PR #2750 is required, or else the roundtrip test will fail.

Summary of changes

set default version of jsonld context and parser to version 1.1 Serializer doesnt have itself an option for this.
version now a parameter for the jsonldparser.parse
default versionnumber in context now shown
autoformat with black on jsonld parser

Checklis

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.(See above)
• If the change adds new features or changes the RDFLib public API:
  • Created an issue to discuss the change and get in-principle agreement.
• If the change has a potential impact on users of this project:
  • Added or updated tests that fail without the change.
  • Updated relevant documentation to avoid inaccuracies.
  • Considered adding additional documentation.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[coveralls]

coverage: 91.019% (+0.01%) from 91.009%
when pulling 461d7af on WhiteGobo:jsonlddefaultversion11Issue2606
into 27c81f0 on RDFLib:main.