Detrusty

- Add switch for exiting when checking endpoint accessibility

- Fix reading RDF-based configuration
- Update dependencies in Dockerfile

- Add feature for defining the source descriptions in RDF
- Create source descriptions in RDF
- Read source descriptions from RDF
- Deprecate JSON-based source descriptions
- Update documentation

- Add query timeout feature
- Docker: update Python

- Update dependencies
- Flask
- requests

- Add physical operator NestedHashJoinValues (NHJV)
- Add physical operator NestedHashOptionalValues (NHOV)
- Use NHJV and NHOV for nested hash join and nested hash optional instead of their FILTER variants