Saving JPEGs with Image IO

[build 0031] JPEGs now work again.

Fixing the problems in the JPEG images fell out in the wash. It looked like a byte ordering problem combined with a pixel size problem (which would explain the vertical striping) - but I did not look into it. Instead I used Image IO to generate the JPEG. The save, using Image IO, fell out in four or five lines of code. Using Image IO means that the OS will handle all the byte order, pixel order, packing etc - all I need to do is to feed it a CGImageRef. As all bitmaps in the OSX version of Cello are now CGImages this is natural. Also as a tiny fringe benefit using Image IO also means that I have been able to remove the JPEG library from the project build, so the file count and build time are modestly improved.

All that remains, to put the issue of bitmaps to rest, is to work through the remaining problems with the other bitmap formats that are not encoded as JPEG. This would seem to be more of a handle turning exercise - there is code missing for the 16-bit indexed bitmap and there may be byte/pixel ordering issues for the 32 bit. Byte/pixel ordering issues happen because the original code expects certain byte orders and I need to move this over to using the more general pixel unpacking code that now exists in the project.