added gang property to each motor

the checkboxes now update the which gang a motor is or is or is not in
(i.e., numbers 0, 1, or 2)
next we should add two new control boxes, one for each gang, w/
direction and speed controls (avoiding rotation display, since that
will still be unique to each motor)
added gangs 1 and 2 controls (not hooked up yet)

added gangs 1 and 2 controls (action functions on button-clicks aren't
hooked up yet, which i think we should do after the individual motors
are all working how we want)
gang motor speeds are in degrees/second. we'll make this similar change
for the individual motors soon
Merge branch 'John'