raise wall hight by 2/16 and use disconnected tops

Default wall pillars are 16/16 high and wall connectors are 14/16 high.
This results in walls not being stackable because there will always be
a 2/16 gap between the walls caused by the 2/16 missing on the below
wall in relation to the above wall.

Since there are no “connected top left”, etc. nodeboxes there have to be
other solutions used to close the gap.

One solution is making the wall bottoms 2/16 longer on bottom to close
the gap to below walls. But this also results in walls penetrating the
ground which might not look good in all cases (no ground below wall and
other combinations of walls and nodes).

I decided to make walls 16/16 high and use a disconnected nodebox on the
pillar that is 2/16 high. So overall “SD Walls” walls are 2/16 higher
but in return they neatly close up all gaps without “nodebox trickery”.

The additional 2/16 high nodebox is not part of the hitbox because
otherwise polacing something on the pillars would result in placing it
above the pillar since the tops reach into the above node.