Use inclusive comparison for thresholds

InteGraality has two 'threshold' concepts,
for groupings (at least N elements belonging to the group)
and for property usage (at least N elements using the property).

These are defined as "at least", but this translated in the SPARQL
as a strict comparison HAVING (?count > threshold), while an
inclusive comparison would make more sense, matching reasonable expectations.

Bug: T224226