Exact phrase searching

[rosnfeld]

This is complicated because we can't use postgres's regular full text search, as it's storing a reduced version of the document. We'll need to do something like:

• if there is a phrase as part of the search, separate that out and use some sort of traditional "LIKE" based query to build its results
• apply negation to that phrase if necessary
• combine its results with those of the regular full text search (using AND)