[MLLIB] [spark-2352] Implementation of an 1-hidden layer Artificial Neural Network (ANN)

The code contains a multi-layer ANN implementation, with variable number of inputs, outputs and hidden nodes. It takes as input an RDD vector pairs, corresponding to the training set with inputs and outputs.

Next to two automated tests, an example program is also included, which also contains a graphical representation.
I think the convergence is parameter in the constructor and you are setting it for the optimizer ```setConvergenceTol(convergenceTol)```. Is this comment still valid?