Improved bilateral filter performance

More than doubled the performance of the filter and correct a bug in the OpenCV version that resulted in flashing from a race condition. Currently the window size is hard coded as 9x9, some experimentation showed this to be a good size with still great performance. Can now run this at 40 iterations.

Further experiments are to include:

• using max colour distance encountered in a direction, I know this reduces bad values (but also density)
• perhaps weight by colour distance with corresponding pixel in right image? If a disparity would result in a high colour inconsistency then probably that should get a low weight?