Remove APICameraSystem::cameraCount

It's already saved in the std::vector.
Start implementing camera calibration
Add some documentation
The API application is a library, not an executable
Implement adding/removing APICamera listeners
Refactor APICamera::remove*Listener functions
Implement APICamera's calibration data functions
Implement APICameraSystem's camera getters
Add camera initialization methods

Actual service sending is not done yet.
Fix APICameraSystem calibrated getters
Implement APICamera::initialize
Add APICamera::sendPictureActivation

I accidently implemented the wrong message - we might not actually
need this method %)
Implement APICamera::startCalibration
Implement Picture receiving for APICamera
fixed build errors
Merge branch 'dennis'

Conflicts:
	src/API.cpp
	src/API.hpp
Merge remote-tracking branch 'origin/camera'
Added Camera Adder
Adapted Lukas' code to match Dennis's code