If the player places table legs, and then places a tabletop while
pointing at the legs (from any side), the table and legs will
automatically be combined into a single node that can then have
something placed on top like usual.
This also gets rid of those redundant "utility" table nodes, since
these have always basically just been a set of legs, and a copy
of the small square wood table. Now they're merged into the above
feature, and aliased as appropriate.
Tecccccccccchhnically, wood legs should only have been allowed to
combine with wooden tabletops... then I googled around a bit,
and found a number of glass tables with wooden legs that were
surprisingly similar to the in-game versions.
