Removed IFace3 and IFace4

Removing IFace3 and IFace4 keeps it closer to the JavaScript version and I didn't find them to add much help over declaring "var face;" At runtime there is of course no difference since the types are not used.

I did try to let Face4 inherit Face3 which was possible, but then all "is" checks have to try "face is Face4" first, since by definition a Face4 is-a Face3 in that case.

Anyways, let me know what you think about this change. No hard feeling if you feel the interfaces are beneficial ;-)