Add Maestro speed/accel parameters

The Maestro API includes these parameters, but the values appear
pinned at speed=100 accel=5.

This patch adds new fields, active only when Maestro is selected,
for the speed and accel parameters for pan and tilt.

Fixed (?) the tab order while I was in there.
Merge pull request #662 from mmiers/pull-req

Add Maestro speed/accel parameters