AP_Camera: removed 3 camera trigger types that do not work

the trigger by wp distance, trigger with throttle off and trigger a
transistor all don't work, and are not structured correctly, plus are
dangerous.

The existing relay support can (correctly!) handle the resistor case
without hard-wiring a pin. The "turn off throttle to trigger" idea is
badly broken, it would crash a copter if it worked. We can make it
work properly on planes if there is demand. As it was it didn't work
anyway. 

The triggger by wp distance method was broken, and had no way to
initiate a trigger anyway
Plane: use update_aux() for setting up extra channels
Plane: make wp_distance static

removed hack in AP_Camera library
Copter: make wp_distance static

removed hack with AP_Camera library
Rover: added full camera and mount support
Rover: moved camera parameter indexes

this prevents a conflict with some old parameters
Rover: fixed dead-zone on throttle
Rover: fixed HIL build
Rover: update to 2.43beta2