simplify MNIST3LayersNNExamplePlan>>#initializeLearningGraph a little. Make more evident the code duplication
simplify MNIST3LayersNNExamplePlan>>#initializeLearningGraph a little.
Make more evident the code duplication

Cuis-Smalltalk/Machine-Learning,Cuis-Smalltalk/Machine-Learning,Cuis-Smalltalk/Machine-Learning