Add "title:..." support to the Ferret engine

Summary:
Ref T12819. Adds (hacky, hard-coded) field support (for now, only for "title").

I've written this so title:quick ferret is the same as title:quick title:ferret. I think this is what users probably mean.

You can do the other thing as ferret title:quick, or title:quick all:ferret.

Test Plan: Searched for title:x, title:"x", title:~"x", etc. Searched for "garbage:y", got an exception since that's not a recognized function. Searched for title:x y, saw both do title search.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12819

Differential Revision: https://secure.phabricator.com/D18503