Fix for face recognition bounds bug

The face recognition box could extend beyond the edges of the image, so
parts of images were being padded with black. This looked odd. This fix
ought to cure that (it’s currently untested for want of a working
Raspberry Pi)
Merge branch 'FaceDetect-Fixes'
This addresses the issue where if a viewer is very close to the camera, their portrait will have black borders around it.
The solution is to enforce the cropped image to remain within the borders of the original image as it came from the camera.
Edit to the loadFiles() function to catch an error that occurs when the image we're trying to load is corrupted (e.g. by the power being cut whilst the image was being saved)
Bug fix (as previous commit to fix issue #1)