Initial work on test cases for history contents API.
Include root folder id in output when creating library.
This prevents the need to hit the API one more time to get the root folder ID before creating datasets/folders/etc... in the library.
Include LDDA state in library dataset to_dict.
Needed to monitor library dataset uploads (in particular for API tests, but really any monitoring will benefit from this).
Infrastructure for library API testing.
Doesn't really test libraries extensively, but adds enough infrastructure to enable a library dataset to history copy test via API.
Start rework of API test mixin TestsDataset into an plain object.
Mirroring the newer WorkflowPopulator and LibraryPopulator.
Rework history.contents_iter to potentially support multiple types.
This is utilized downstream in collections work to allow a similar API to be used for loading HistoryDatasetCollectionAssociations as HistoryDatasetAssociations.
Rework history_contents API to allow room for multiple 'type's of history contents.
Downstream dataset collections are being added and can be associated with histories. They have hids, can be deleted, etc... many of the same properties as HDAs. This refactoring "makes room" for these in the history contents API by allowing type to be passed in.

Since HDAs and HDCAs can have the same id - the path history/{history_id}/contents/{contents_id} is somewhat ambigious - so this changeset adds the path history/{history_id}/contents/datasets/{history_dataset_id} while a matching resource path downstream history/{history_id}/contents/dataset_collections/{history_dataset_collection_id} has been added.

The vanilla contents path remains but should be considered deprecated IMO.

Adding type parameter to history/{history_id}/contents index route - this will always default to dataset for backward compatibility - but downstream can be specified as either dataset, dataset_collection, or "dataset,dataset_collection".
Merged in jmchilton/galaxy-central-fork-1 (pull request #342)

Refactor History Contents to Support Multiple Types