Add AES2501 driver

This driver works quite nicely. Seems a little too sensitive though (too
much black in the standardized image, not enough ridge gap definition).

Processing results are quite good, but you need a good enrollment image
(i.e. long!). It's best to get such images by pressing harder than you
might think necessary and swiping slowly.

libfprint/core.c

@@ -334,6 +334,7 @@ static struct fp_driver * const primitive_drivers[] = {
 
 static struct fp_img_driver * const img_drivers[] = {
 	&uru4000_driver,
+	&aes2501_driver,
 	&aes4000_driver,
 };