* Optimize Elasticsearch fullword field
Since the main display_name field ngrams words up to 15 characters,
anything to and under that will already be indexed - the fullword field
(which we have for words longer than 15 characters) needs to index only
words longer than that.
* Preprocess ES terms for better literal matching
This commit adds a new .exact subfield to display_name, which holds a
barely-filtered version of the original title we can do "literal"
matching against. This is not real substring matching, but quoting
terms now actually does something!
Implements a simple preprocessor for the search terms to extract quoted
parts from the search terms, optionally prefixed with - to negate them.
The preprocessor will create a query that'll join all three query-types:
the simple_query_string, must-phrases and must-not-phrases.
This fixes searching for "Machiavellianism", 16 chars ("Machiavellianis", 15 chars, worked previously).
Does not (seem to!) break anything, but requires a re-indexing of ES.
