3 lights ( + material and shader injection) implemented and tested on ios, android and rasberrypi

Lot of changes. Please review
With the current implementation, it seems lights are only "owned" by the Scene object, so it makes sense to make this a vector of unique_ptrs. However after having a chat with @patriciogonzalezvivo, he mentioned that for a UI control light objects could be shared!... I wanted have others opinion on this though.