Sensor width seems to be only 128 pixels and that's not enough
for scanning whole finger surface. Lower bz3_threshold to 25,
since for wrong finger score never goes above 10, but sometimes
for right finger score is below 40.
Some scanners provide hardware assistance in frame assemling, i.e.
horizontal and vertical offset to previous frame is provided. This
commit improves code to utilise that assistance. Sensors without
hardware assistance will use software algorithm, which was also
improved to do search in horizontal direction.
