DepthMap slow or red bar or crash

You can speed up the Depth Map process. Here is what you need to do:

Increasing the Downscale factor will speed up the process and may resolve a red bar error, but will reduce the precision.

Reducing the number of T cameras (sgmMaxTCams (Semi Global Matching: Number of neighbour cameras), refineMaxTCams) will directly reduce the computation time linearly, so if you change from 10 to 5 you will get a 2x speedup.

A minimum value of 3 is necessary, 4 already gives decent results in many cases if the density of your acquisition process regular enough.

The default value is necessary in large scale environment where it is difficult to have 4 images that cover the same area.(#228)