WMR auto exposure and gain module for better tracking

This MR introduces an auto exposure and gain module and uses it for the WMR driver. Wrong values of exposure and gain can make or break the SLAM tracking, hopefully this will help with that. Right now the way it works is pretty simple, it just tries to adapt the image histogram mean. I tried implementing fancier ideas but unfortunately none of them worked as well so for now I'm sticking with this.

Here is a 2-minute video of the module in action.