Camera support?

I'm coding camera control and geotagging. Would you like to add camera classes to dronekit? Would you like a PR?

Here's my first working code: https://github.com/antonvh/dronekit-python/blob/gopro_wifi/dronekit/cameras.py

Would I add a camera object to the vehicle class? Or a vehicle object to the camera class so the shutter can log gps data?
