Fixed activation function gradient and SmoothNet plotting

Corrected the backprop in normalized, rectified Huber activation (#7)
in ActFun.m. Changed default plot in SmoothNet to training set loss.
Significant changes, to make LDNet more usable

Added a correct implementation of normalized ReHu to LDLayers. Cleaned
up LDNet code a bit, changed it's default plotting to training set loss
and added weight/bias fuzzing.