STY: Change ITK_OVERRIDE for override in whole code (find Modules -type f -exec sed -i 's/ITK_OVERRIDE/override/g' {} +)

application module

BUG : SOMModel now herits from MachineLearningModel<TInput,...> instead of MachineLearningModel<itk:variablelengthvector<TInput>,...>

DR is now based on Machine Learning Models, it is now possible to reduce de dimension of the pca model (it has to be changed in PCAModel.txx for now

Sparse ae added, parameters can now be defined for each layers (noise, regularization, rho and beta)