Rawspeed SRW new encoding

Ported the newest type of SRW encoding from dcraw. Klaus will probably want to do the decoding differently, using more of the existing rawspeed code.

Added support for the NX3000. I've compared the output and it seems to be identical to the dcraw one. However the demosaiced image has a green tint. I've tried different CFA patterns with not luck. Not sure what the problem is.