retire junglegrass- and dry shrub-based plastic recipes, those nodes
are becoming too rare to use for this now.
fir crash in flip door routine if param2 is nil
Change recipes to use wood group.
split signs_lib from homedecor, put them into their own separate mods
package the two together as a modpack so that regular homedecor users don't
see a functional change, but others can take signs_lib and use it as a
standalone mod.

also get rid of some *~ files
fix crash
fix crash, try #2
move signs textures to the right mod
make the signs textures a little darker, more saturated, so that they
stand out better against default wood.
git a little overzealous on the recoloring of the signs textures - forgot that
the posts need to remain plain-wood-colored.
that time I was a little UNDERzealous with the coloring of the signs :D