EMI: Fix actor orientation

I think I finally managed to set the actor orientation issues in EMI straight, although I have to admit that I mainly tried to negate angles and coordinates in random places until all LUA functions did what they were supposed to do. ;-)

The simplified EMI-specific version of calculateOrientation() did not work properly because it only gave the size of the required angle, not its direction. I'm now sharing the full-blown calculation with Grim, with an added coordinate swap to convert between the two engines' coordinate system. All other diffs are in EMI-specific places, so there are no changes affecting Grim.