laser_lines: use PCL 1.6

Use Fuerte PCL 1.6, fixes segfaults.
laser_lines: fix line clustering
landmark_frame: only update while moving and briefly afterwards

To prevent jitter in the frame while standing we calculate it now only
while moving and for a few seconds after we stopped.
landmark_frame: update if transform invalid, invalidate out of zones

Update the transform if it is currently invalid independent of the other
threshold conditions. If the robot moves out of a landmark zone,
invalidate the last transform so that it is no longer sent.