ENH: Added new neurons - Absolute, LinearSaturated

include/4neuro.h

src/CMakeLists.txt

src/DataSet/DataSet.cpp

src/DataSet/DataSet.h

src/Neuron/NeuronAbsolute.cpp

src/Neuron/NeuronAbsolute.h

src/Neuron/NeuronAbsoluteSerialization.h

src/Neuron/NeuronLinearSaturated.cpp

src/Neuron/NeuronLinearSaturated.h

src/Neuron/NeuronLinearSaturatedSerialization.h