Add implementation of Wavelet Neural Networks

[mandar2812]

Reference: Wavelet Neural Networks - David Veitich

This task is broken into two parts.

1. Implement WaveletNetwork class based on pseudo code outlined in sections 3.2.1.1 and 3.3.1
2. Implement WaveNet class based on sections

For both parts use the Wavelet[I] API to represent Wavelon object instances for multivariate inputs, which have parameters that can be calculated using the GradientDescent class. Implement WaveletGradient and WaveletUpdater classes by extending Gradient and Updater.