InteractiveBase implementation

@basvandenheuvel , @PimV, @JohanBeekers
feedback verwerkt
implementation of the feedback
made interact pure virtual
placed InteractiveBase in Entity folder
Update InteractiveBase.h

revomed #include "sdl.h"
Update InteractiveBase.cpp

added white line on file end
Merge pull request #38 from PimV/BaseInteractive

Base interactive
@PimV and @JohanBeekers both agreed