* combine rotation functions -- one no longer needs to choose
a particular rotation function for the node's paramtype2,
it'll figure it out automatically.
* fix glitch in wallmounted rotation
* re-order rotation facing order to N, E, S, W, floor, ceiling.
* limit yard sign to simple NESW-only rotation
* allow rotation of hanging signs (NESW only)
* allow rotation of signs on poles/posts if there's nothing in
the way of where the sign has to move to (NESW only).