LP#2004055: Simpler Display Field highlighting

LP#2004055: Simpler Display Field highlighting

This commit uses database functions to precompute the normalized and
tokenized tsquery required for highlighting before it is returned to the
user, and disallows highlight-time compilation of the highlight map.
The primary purpose of this is to avoid the chance for user input to
find its way directly into SQL statements, but an additional benefit is
that it becomes much simpler for high level application code to make use
of Display Field highlighting in non-search contexts.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>
Signed-off-by: Jason Boyer <JBoyer@equinoxOLI.org>