Verification of a disparity map and silent mode.

Added:
- option to pass a ground truth disparity map to compare results to; only for static images;
- option to suppress displaying any pictures and waiting for keyboard input; only for static images;
- ground truth disparity images for test pairs;
- class for comparing disparity maps;
Changed:
- tweaked a bit the way disparity is fit into gray-scale images; work in progress.
Fixes and development.

Fixed:
-strange behavior when passing negative numbers (-1 and -2) to SGBM being misinterpreted as parameters rather than numbers;

Added:
-measuring time it took the algorithm to complete

Also made a change to the way resulting disparity map is transformed into picture.