Added jpeg decoder jpegp.c using RAINBOW lib. Currently enabled only for pictures not supported by old decoder (as old decoder more optimized for low mem targets)
Someone TODO:
* Old decoder has optimized downscale logic which new decoder doesn't have (it gives big difference in required memory and time for decoding). This logic should be ported/adapted if possible.
* Add smooth downscaling.
* Grayscale support
Change-Id: Ie96bc62848b51cc6a3942f8e069ec6ab02dc1c56
