Added support for float weights in CM_WeightedRandom
Added method CM_Model_Splittest::setVariationWeightList() to set weights at runtime
Added tests for weighted split tests

- Added exceptions in setVariationWeightList()
- Added tear down method for simplicity
- Docu
Thrown Invalid instead of Nonexistent in setVariationWeightList()

- Adjusted test
Docu
Small refactoring
Refactoring: Introduced helper method CM_Model_Splittest::_getVariationRandom()
Merge pull request #1284 from fauvel/issue-1284

Weighted split tests