moved servo pin back

..because pin 5 isn't that useless

also rearranged some bits
fully working

I'm not entirely clear why this version works and the previous version didn't (it was behaving like the focus pin was always pulled low).

The changes that I'm aware of:

1. Using spaces instead of real tabs for indents. Why does the Arduino IDE hate tabs?

2. Eliminated use of `led_pin` and replaced it with separate `shutter_led` and `focus_led` constants, even though they point to the exact same pin definition.

3. `safety_pos` constant is defined earlier, and a few other things are slightly moved around.