[modules] rewrite cam_control to use gpio instead of led
[modules] gpio_cam_control: fix dox
[gpio] use gpio instead of fake led

power switch as gpio
update board config files
[gpio] use new cam gpio definition
fix POWER_SWITCH_GPIO
[modules] update ROTORCRAFT_CAM_SWITCH_GPIO handling
[lpc21] simplifly usb_tunnel, fix LED usage
Merge pull request #652 from paparazzi/cam_control_gpio

Use gpio functions instead of abusing fake LEDs.

e.g. for cam_control:
use <define name="DC_SHUTTER_GPIO" value="GPIOC,GPIO12"/> instead of <define name="DC_SHUTTER_LED" value="7"/> with LED_7 being defined somewhere else...