Add facet results to getCollectionItems use case

[ekraffmiller]

For the SPA Q4 feature "Collection Page: all filtering options", we need to get the facet results for the Collection Page.

To get this data, we can use the use show_facets=true param in the Dataverse Search API.
The getCollectionItems use case should be updated to return this data, possibly by adding a boolean field showFacets to the CollectionSearchCriteria object.

[g-saracca]

Closing as it will be addressed in #229