Issue #30: An initial (although a bit greedy) fix, based on selecting
the first available column and sorting on that.
Added method to PerformanceCharacteristics that will enable datastores
to indicate if natural ordering is OK for pagination or not.
Issue #30: Fixed selection attempt based on primary key and likely
column names.
Fixed compile issue downstream
Merge pull request #31 from datacleaner/issue30

Fix for #30