Allows rotating things like signs and torches. Axis rotation
rotates over all 6 faces, face rotation flips upside down to
flat on floor only, and of course in the 4 horizontal directions.
Made the code a bit more modular to account for different rotation
schemes. Should be easier to extend from here on to other needs,
and the functions can be reused by other mods for convenience.
Other screwdriver mods, or mods that cause rotation, might operate without the screwdriver mod loaded and have `screwdriver.disallow` unavailable.
This allows nodes to default to full-disallow rather than full-rotation in such a situation.
This prevents nodes that are not of the "facedir" paramtype2,
as these are generally not expected to be able to rotate. Mods
and other methods may still manipulate param2 of these nodes
as expected.
Addresses #712
The message to "hold shift" makes an unwarranted assumption about the
user's keybindings. Messages from the server should refer to a key's
game function, rather than its extragame identity.
