Faster 2D-Hadmard Tranform

Fast 2D-Hadamard/Walsh Transform based on Simple Matrix Vector Multiplication

This function generates the 2D Walsh or Hadamard Transform of a matrix.
Where the Walsh Transform uses the sequency ordered matrix and the Hadamard the natural/hadamard ordered matrix.
The paley ordered transform is not yet implemented.

On my machine the function can transform matrices of a size up to 4096x4096 in very little time compared to the other 2D Walsh/Hadamard transform (ID 6882) which needs substantially more time.
For a 4096x4096 the transformation takes ~30s on the first call and ~20s after that (Transformation matrix is cashed)

References:
Walsh functions:
http://mathworld.wolfram.com/WalshFunction.html

Howto generate sequency ordered Hadamard Matrices:
http://ieeexplore.ieee.org/iel5/12/35157/01674860.pdf

http://dx.doi.org/
doi:10.1016/j.physletb.2003.10.071