This is a follow up to CATS-897.

We have two methods now to get files within a dataset. One returns all datasets containing the file but not if the file is in a folder. The other returns datasets containing the file independently of whether the files is in a folder or not. This is due to the original implementation of the first method and the assumption that the controller's action would take care of looking into folders. This seems counter intuitive and confusing.

We could just adopt the second method in all actions. This would also help clean up some of the complexity in the actions.