Geoff+Tegan+JC:>back propagation algorithm implemented, as well as a switch from depth first to breadth first
	modified:   Neurons/Brain.cpp
	modified:   Neurons/Brain.h
	modified:   Neurons/Connection.cpp
	modified:   Neurons/Connection.h
	modified:   Neurons/InputNeuron.cpp
	modified:   Neurons/InputNeuron.h
	new file:   Neurons/Layer.cpp
	new file:   Neurons/Layer.h
	modified:   Neurons/Main.cpp
	modified:   Neurons/Neuron.cpp
	modified:   Neurons/Neuron.h
	modified:   Neurons/Node.cpp
	modified:   Neurons/OutputNeuron.cpp
	modified:   Neurons/OutputNeuron.h
	modified:   Neurons/Playground.cpp
	modified:   Neurons/Playground.h
	modified:   makefile