+This query builder is very limited, it should be replaced with DBIx::Class
+or similar very soon
+Meanwhile adding support for special key '' in case of a data_hashref to
+support filters of type
+
+ ( f1 = a OR f2 = a ) AND fx = b AND fy = c
+
+Call for the query above is:
+
+ SearchInTable($tablename, {'' => a, fx => b, fy => c}, $orderby, $limit,
+ $columns_out, [f1, f2], 'exact');
+
+NOTE: Current implementation may remove parts of the iinput hashrefs. If that is a problem
+a copy needs to be created in _filter_fields() below
+