"nullOnly" from SpatioTemporalStructure/Interval.hs now works on lists
containing multiple empty intervals.
Fixed a typo in DecisionProcedure/Opus/TriangleConsistency.hs.
Changed Benchmark.hs to include a combined version of
TriangleConsistency without and with witness (This is for my next paper
and should actually be in a different branch. Sorry.)