public org.bukkit.block.BlockFace calculateEnterFace(org.bukkit.util.Vector position,
Calculates the face of this AABB that is first entered when moving in a direction from a position.
The movement is that of an infinite line. The face direction first hit is returned. The position is
relative to this AABB (the rails).
position - x/y/z of the position relative to the block
direction - x/y/z of the direction in which is moved