Quilt module: if cached data is not available, generate what we can from the index

[nevali]

If there is no cached data (e.g., because a proxy has not yet been generated) for an entity, Quilt should generate summary information from the RDBMs index — which will at a minimum contain the coreference data.

This may also occur due to #105 (and hence #87).

The actual RDF-generation logic for this ought to be shared with #35.

Internal tracking: RESDATA-1110