Make sure the proj mtx calib subdir exists

A nonexistant directory caused the camera to block, which in turn
created a timeout.

I also added a spinbox for the intensity step when calibrating the
projector inverse transfer functions so we don't have to wait for
each intensity to be captured.
Add options for camera calibration

This is mostly just layout additions. None of the controls actually
do anything yet.
Allow selective calibration
Implement using the options during cam calib

One thing I had to do in order to support printing each iteration
was to make the check box static so that it could be polled from
the error method, which has to be static for powell to use it.
Skip pixels with over-exposed channels in mtx imgs

Even if no pixels are over-exposed when all three channels have the
same intensity, there can be over-exposed pixels when the channels
are not equal. I've added a statement to skip any over-exposed pixels.
It might be better to re-take the images if any over-exposed pixels
are detected, but that would be a little more complicated.
Add options for the projector transfer functions
Add an option for color mixing matrix calibration
Update Doxyfile to hide source code from documentation