WIP: more modular detection system

This MR introduces the REGISTER_DETECTOR( void (*func)() ) macro, which may be used to register detector functions into a singleton ResourceManager object. The registered detector are then enumerated in OpenRGB.cpp:DetectRGBControllers. This approach makes it more scalable to add/remove detectors.

The global ResourceManager also becomes responsible for keeping track of i2c_smbus_interface, and RGBController instances.

Origin: #420 (closed).