Added CascadeNetworkWeightShift and unit test.

Measures the shift in weights in a cascade network.
Added PerExpansionNNPerformanceChangeStoppingCondition.

It similar to NNPerformanceChangeStoppingCondition, but is only
performed when an expansion in the NN architecture is detected.

Changed dynamicPSOCascadeNN.xml to incorporate the new stopping
condition.
Merge pull request #143 from censlin/cnOldWeightChangeMeasurement

CascadeNetworkWeightShift and test.
Merge pull request #144 from censlin/cnExpansionStoppingCondition

Added PerExpansionNNPerformanceChangeStoppingCondition.