Contourlet transform toolbox

Modified from: https://github.com/mazayux/pycontourlet

Changes:

• Renamed /pycontourlet folder to /pycontourlet4d to support multi-channel PDFB decomposition on batches of images (original code only supports single channel, single imaage operation). The following changes are made:
  • Replaces signal.convolve with PyTorch's F.conv2d, which is faster and supports 4D tensors (batch, channel, height, width).
  • Rewrite resampc.py with Cython instead of weave, which is not supported in Python3.
• This result in around 15% speed up in training.