gui conf: check that the calibration values read are possibly correct

The calibration values should be written by Odemis, but the user might change them...
so check them.
It will avoid to fail much later in the GUI, for unclear reasons.
Set blank mode in imaging
Small fix in resolution values
Number of frames not power of 2
Merge branch 'kimon-MiniCalibration' of vpn.delmic.com:odemis into kimon-MiniCalibration