Cmem-plugin-validation

Changed

- update `Validate Entities` plugin documentation

Changed

- hookline
- dependency updates

Added

- Task to validate entities or JSON datasets with a JSON Schema

Fixed

- correct transformation of SPARQL code to string

Fixed

- allow for selecting system graphs (e.g. custom shape catalogs) for validation

Added

- flag to output violations as entities (fixed schema port)
- advanced parameter to provide a custom resource selection query
- custom icon
- proper task tests