model includes a flat extension on one "side" to fix #342
rotate the reactor with the screwdriver with shift-right-click before filling, to
line up the flat side with your cabling. Note that the reactor doesn't actually
care which side the cable comes from.
Note: this required renaming the base node name for the oblate spheroid
object, which previously had been named simply "sphere". The result is
that all such nodes in an old world will change to actual spheres.
Since this includes a formspec change, machines will have to be dug and
re-placed to get the new program button to show up, and/or if the image
on the Oblate Spheroid button shows wrongly.
