Add Monitor.getMatchingQueries()

This is useful for presearcher debugging - give it a document, and it will
return a list of all the queries that the presearcher selects as candidate
matches.
Add toString to DocumentMatches.MatchStats
ANY token in extractor should include its source term, for help in debugging
Prefer longer terms in boolean extraction

Longer terms are less likely to appear, in general, so given a choice of several
terms in a conjunction, extract the longest one.