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
Since written books are quite different from empty books, the
visual clue that they are different items is really needed in-game.
I've added a "clasp" or "belt-with-buckle" like element to the
png from default_book, keeping them very similar but also
immediately recgnizably different.
I added the new texture to blockmen's license list since it's
obviously derivative of his work.
The PNG was run through a minimizer/optimizer to save space.
Auke Kok