Camera exposure value preferences need to be per-camera, not per-system

[jackjansen]

Currently the exposure and other values are for all cameras. This is wrong, because it actually defeats the purpose (adjusting per-camera lighting conditions.

We need to add a per-camera element where we set per-camera settings. We also need to think which settings are global and which per camera. We also need to rethink which ones go into system, postprocessing, depthfilterparameters and the new per-camera element, and why.

Finally, for the kinect caerma settings, "-1" means "don't touch" for some parameters, but "auto" for other parameters. This is a bad idea. Auto needs to be its own value.

Problem is worst with the top camera, but also with others.

cc: @C-Cortes-spa