Changes the behavior for the PlanOperation::distribute() method

Now the out paramers will be start and end with end be one after
the acutal element so it can be used as in traditional while x < end
comparisons
Merge pull request #22 from hyrise/feature/table_partitioning

Changes the behavior for the PlanOperation::distribute() method
Merge branch 'master' of git://github.com/hyrise/hyrise