Fix sBIT in 16 bit for PIL
Replace hex pngsuite with original file (also more complete and fresh)
Add raw iccp support (tests required)
Rescale 16 to 8 within purepng as PIL does not support RGB 16bit/ch
https://github.com/python-pillow/Pillow/issues/914
'almostEqual' comparation for images
Rescale transparency when rescale image
Workaround with incorrectly saved transparency