The Powernet Crusade

Ports additional powernet changes from /tg/, mainly concerning the SMES, machine processing, and area power updates.

Our APC load balancing is again a victim but the current processing is more release-friendly than my previous attempt. My previous attempt worked fine as long as there was enough power. If not, things got extreme fast.
Also aware that one (autoflag != 0) check is lost.

Will continue work on correcting this.
I'm not sure which flag you are referring to, but the profiling stuff is useless clutter now that there's actually nothing to profile.

The same thing could be said of ```/obj/machinery/proc/update_use_power()``` as well, although I guess it doesn't hurt to keep around. 

Lastly there's a lot of atmos machine code (and other machine code -- pretty much anywhere we use ```update_use_power()```) that can be simplified now that we don't need to worry about triggering area power updates.