backprop with momentum term
renamed error to gradient

implemented learn rate decay
Merge branch 'master' into NetworkFactory

Conflicts:
	backprop/backpropnetwork.cpp
	backprop/tests/backproptest.cpp
	quickprop/quickpropnetwork.cpp
	quickprop/quickpropnetwork.h
	quickprop/quickpropneuronlink.cpp
	quickprop/tests/quickproptest.cpp