Refactor entityhub.query.clerezza module

The entityhub.query.clerezza module currently contains the

1. FieldQuery to SPARQL mappings
2. Clerezza specific implementations and utilities for ResultLists ....

For the implementation of the SesameYard (1) is required, but a dependency to Clerezza is sub-optimal.

Because of that all SPARQL generic features should be extracted to a new entityhub.query.sparql module. Clerezza specific extensions should stay in the entityhub.query.clerezza module. Maybe also introduce a entityhub.query.sesame module with similar functionality as the clerezza one.