Add example for oculus interface

Important things about using sfml-oculus with bci-interface:
- OpenGL objects work in a very different way, it's untested and probable that
  usual bci-interface OpenGL objects won't work here
- Drawing is done in an up-scaled 640x480 window, the proper scale can be
  obtaiend through calls to your BCIInterface instance as soon as the
  InitOculus has been called or after OculusDisplayLoop was started, this is
  shown in the example.