added a new proc for atmos machinery, nullifyPipenetwork(). As their name says, it will nullify the references of a pipenet network datum.
Added qdel for pipenet network datums, this removes most of the singularity lag.
Makes datums work on the garbage collector.
Updated heat pipes, red pipes, manifolds and normal pipes icons to show completely disconnected pipes.
Allows the heat exchanging pipe to be wrenched without having anything to connect it to.