machinery_process() & auto_use_power efficiency tweaks (#2657)

changes:

Machinery now uses machinery_process() instead of process(), allowing machines to be put into SSprocessing-style lists in addition to the machinery list.
Automatic power calculations now involve less proc-calls.

code/modules/research/server.dm

@@ -50,7 +50,7 @@
 		for(var/N in temp_list)
 			id_with_download += text2num(N)
 
-/obj/machinery/r_n_d/server/process()
+/obj/machinery/r_n_d/server/machinery_process()
 	var/datum/gas_mixture/environment = loc.return_air()
 	switch(environment.temperature)
 		if(0 to T0C)
@@ -147,7 +147,7 @@
 				server_ids += num
 		no_id_servers -= S
 
-/obj/machinery/r_n_d/server/centcom/process()
+/obj/machinery/r_n_d/server/centcom/machinery_process()
 	return PROCESS_KILL //don't need process()
 
 /obj/machinery/computer/rdservercontrol