Remove old queryFacts and insertFacts paths

[ongardie-ebay]

There's a large amount of cruft in the API server to support the old way of doing queries and inserts. It might also be confusing to newcomers.

[ongardie-ebay]

#17 removed insertFact. queryFacts is still there, and may still provide useful functionality. We should think about whether we can port it to KGValue (so that we can remove api.KGObject), and whether it needs its own RPC (or can we fold it into query with a new keyword)?