ENHANCEMENT: Making Exclude Children 3.1 ready

In 3.1 you can not longer write $dataSet->filter(); $dataSet->exclude/filter/whatever

As the original object is not longer changed and instead, methods like filter return a new clone with the new filter/exclude/whatever added.
Merge pull request #2 from sunnysideup/patch-1

ENHANCEMENT: Making Exclude Children 3.1 ready