Adds support for creating, updating and deleting resources. CRUD on resources is now implemented. There is just one limitation: If you update a resource which has a to-many relationship but you don't updated that one, the relationship is neither included as related link nor as resource linkage.
Adds support for sort (descending, multiple fields) and filter on fetching resources.
Including related resources as attributes has been dropped since it's not covered by spec. Therefore include option has been removed and compoundDoc changed behavior. Details are provided in #10.