Replace Filters implementation by specific sql queries

[fm3]

In the wk backend, List queries for datasets and users fetch all accessible items from the db and then filter them according to filter criteria. There are two problems:

• The filter criteria are not explicit GET parameters and thus never appear in swagger annotations
• Unnecessarily many objects are fetched fromt he DB and parsed as jvm objects Instead, we should consider composing specific sql queries depending on the selected filters.