Moved JPEG compression to ImageHandler.
Changed naming of functions in ImageHandler to be more consistent.
Tested successfully with JPEG (iOS) compression factor of 0.5
Added support for One-Shot Mode on iPad in MasterViewController.m
ImageHandler : imageNSDataFromSampleBuffer performs scaling fixed to kShortestSideInPixels (it is not possible to know how the Camera Session Preset works on different devices (iPhone 4/4S, IPhone 5, iPad2,...)
ImageHandler imageNSDataFromSampleBuffer is converting image to greyscale before sending it.