make the wrapper `blockgame.register_node` make reasonable assumptions
that make node registration more convenient.
change other code to take advantage of that change.
also remove the `blockgame.reg_simple_node` utility since it's now
redundant.
move plank registration and recipe out of tree mod into newly created
woodworking mod.
also update plank recipe to require cobblestone instead of stone to be
held while pummeling.