Defined basic interface with MultilayerPerceptron.

Also has been defined the public constructor.
Added Serial version to Serizable interface
Interfaces implemented
Added commenters to the Default constructor
Added a new constructor with comments.

The new constructor initialize the object with a ArrayList<NeuronLayer>
argument
Added the method getLayers.

It returns all the layers into the MultilayerPerceptron in a
ArrayList<NeuralLayer>
Added default copy constructor