Updates of possible interest

[ConradHughes]

Hi Jeff,

Thanks very much for keeping cropgui going. I've a few updates here which might be of interest:

• Use of 'cp' during install invokes umask which can leave unreadable files installed; use 'install' instead.
• I've added a script to create four test images which help verifying correct behaviour under rotations and different JPEG block sizes.
• Also added some extra keyboard controls for processing multiple images at a time: 's' to allow you to take multiple crops from one image, 'n' to skip to the next, and 'q' to quit. Hm. I should probably find somewhere to document these.
• This involved a bugfix to the event handler, where pressing return while processing multiple images would skip on two images rather than just to the next.
• Minor thing, but title/parent parameter order was a bit inconsistent in the file chooser stuff; fixed.

I have another patch which offers correct crop rounding, but am not sure whether it's worth pushing. The current always-round-to-block-size behaviour for all four edges is overly aggressive, in that the bottom and right edges of any crop don't need to be block-aligned, but unfortunately jpegtran itself doesn't handle this correctly for rotated images even if provided with a valid command line. I'm looking into trying to produce a patch for that..