Trim redundant code from TermIndex

NOTE: SpecialItemDisambiguation was previously using
the "fuzzySearch" option, which was then ignored
by the implementation. This is now changed so that
case sensitive matching is requested explicitly.
SpecialItemDisambiguation should have a setting
for enabling case insensitive (and poerhaps also prefix)
matching.

DEPLOYMENT: heads up to ops: keep an eye on wb_terms,
some quries are now constructed differently. This
affects only queries via Special:ItemDisambiguation,
not wbentitysearch, so it should not have much impact.

Change-Id: I47098dd3163a2a7962f2d14d6181181793b9e501
Merge "Trim redundant code from TermIndex"