includes just enough code to try to auto-route them as they're placed.
the "root" node is now the horizontal one - if you have diagonals and
they don't place right, they should after you dig them and place again.
also make shower tray turn off taps above it, if any
minor tweak to particles function to add Y velocity
added more detailed collision boxes to the sinks to accommodate particles
when placing, code will try to determine if the bannister should be
left- or right-sided. Defaults to left-sided; hold shift while placing
to force right-sided.
create it by placing two twins of the same color side by side, left first
also moved the bed extension functions into handlers/expansion.lua,
renamed them, and made a few other minor tweaks to that file accordingly.
