each sign type has a separate table which now defines the nodebox
model and position of the text on that model, instead of separate
sets of tables for each.
MUCH more readable background texture for all signs
use exact-to-pixel dimensions on all signs
move sign models to start of signs_lib where they can be seen
make homedecor's brass/iron signs-on-posts use them
adjust all textures accordingly
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