Fix all undefined references using dummy functions
Don't create a handle before calling ros::init
Use ros::AsyncSpinner to prevent blocking

With the standard ros::spin call, an API consumer would block when
creating the API which isn't what we want.
Automatically find and use all cpp files

Previously, only some camera files have been compiled in.
"Fix" build errors in APIQuadcopter

Some of these have been fixed by commenting out the respective function
or by using dummy return values.
Fix APIQuadcopterListener callback name

We decided to only use "Quadcopter".
"Fix" more undefined references in APIQuadcopter
Implement API::getCameraSystem()
Add dummy implementation in API::launchQuadcopters
Merge branch 'dennis' into guifix

Conflicts:
	src/APIQuadcopter.cpp
Merge pull request #6 from KITrokopter/guifix

Fix linking issues with the GUI