Ref T12819. Depends on D18492. Instead of passing a raw query into the Query layer, parse it first.

This allows the query layer to figure out which parts should be substring vs term match, and would allow the SearchEngine layer to do author:... eventually by picking it out before sending it to the Ferret engine.

Ran some Ferret queries. They work like before, except that nonsense like -+"quack" raises an exception now.