ENH: Added serialization method to NeuronDifferentiable class

src/Neuron/Neuron.cpp

 #include "NeuronSerialization.h"
 
 BOOST_CLASS_EXPORT_IMPLEMENT(lib4neuro::Neuron);
+//BOOST_CLASS_EXPORT_IMPLEMENT(lib4neuro::NeuronDifferentiable);
+
 
 namespace lib4neuro {
 

src/Neuron/Neuron.h

@@ -72,6 +72,13 @@ namespace lib4neuro {
  */
     class NeuronDifferentiable : public Neuron {
     public:
+
+        /**
+         * Struct used to access private properties from
+         * the serialization function
+         */
+        struct access;
+
         /**
          * Calculates the derivative with respect to the argument, ie the 'potential'
          * @return f'(x), where 'f(x)' is the activation function and 'x' = 'potential'