Added more error checking and state information to decoder
Decompression can now operate on 1 byte at a time.
The PNG decoder will also now return on decompression errors.
PNG Deinterlace functions, fix filters and other things.

Added a function to PixelBuffer to output PPM image to assist debugging.
Formats and depths check flipped around.
Truecolor PNG loading tested and working.
Commented out some of the verbose informational messages.