Update PR-655 configuration according to configIN. If no input is provided, return the current
configuration string.
[configIN] can be in form of the string returned from PR655config, or a cell containing values
ordered { Units, Exposure, N Samples, CIE Observer, Sync Mode, Frequency }.
02/09/09 tbc Wrote it.
Psychtoolbox/PsychHardware/PR655Toolbox/PR655config.m