- Moved pipe construction defines into __defines/construction.dm

- Unified pipe *unwrenching* by creating a standard proc along with the `construction_type` var.
- Eliminated the pipe fitting name & icon_state lookup tables by adding `pipe_state` var on atmos machinery and referencing that.
    - Each pipe which can be made from a fitting object should override `pipe_state` with the icon state to be used on the pipe fitting object.
- Eliminated the giant switch statement of doom in pipe construction by delegating that work to `on_construction` proc.
    - To make this work, every pipe must implement `get_neighbor_nodes_for_init` which returns a list of nodes which should be re-initialized on that pipe's construction.
- Combined the SCRUBBERS, SUPPLY and REGULAR pipe fitting classes together by storing the `piping_layer` variable and using the `setPipingLayer` procs
- Standardized the code for searching for node neighbors into the `can_be_node` proc.
    - This proc is also improved in that is a mutual check, `check_connectable` is called on BOTH objects, so they have to mutually agree to connect as nodes. Eliminates lots of special edge case logic.
    - Updated all the `amos_init` procs to use `can_be_node`.  In the most common cases, even that boilerplate code is consolidated into the `STANDARD_ATMOS_CHOOSE_NODE` macro.
- Implemented `pipe_flags` which lets pipes declare (or override) certain requirements.
- Adds a "pipe_recipe" datum to help out things that construct pipes.  By taking it out of the dispenser, we open the road for multiple dispenser types.  No, no RPD yet.  Soon.
    - Enhances the pipe dispenser to operate on pipe recipe datums instead of hard coded lists of pipes it can construct.   These datums are also (partially) initialized from the pipe machine types themselves, reducing having to define stuff in multiple places.
    - Switched pipe dispenser UI to use browse().   Not a NanoUI, but makes it a bit prettier with low effort.
    - Changed pipe dispenser to use a button selector to switch between Regular/Scrubbers/Supply instead of having separate list items.
- Added icon states to HE pipes to support the "connected on neither side" state.

code/ATMOSPHERICS/components/binary_devices/algae_generator_vr.dm

@@ -14,6 +14,7 @@
 	idle_power_usage = 100		// Minimal lights to keep algae alive
 	active_power_usage = 5000	// Powerful grow lights to stimulate oxygen production
 	//power_rating = 7500			//7500 W ~ 10 HP
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 
 	var/list/stored_material =  list(MATERIAL_ALGAE = 0, MATERIAL_CARBON = 0)
 	// Capacity increases with matter bin quality

code/ATMOSPHERICS/components/binary_devices/binary_atmos_base.dm

@@ -30,6 +30,9 @@
 			initialize_directions = EAST|WEST
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/binary/get_neighbor_nodes_for_init()
+	return list(node1, node2)
+
 /obj/machinery/atmospherics/binary/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node1)
 		network1 = new_network
@@ -64,17 +67,8 @@
 	var/node2_connect = dir
 	var/node1_connect = turn(dir, 180)
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,node1_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
-
-	for(var/obj/machinery/atmospherics/target in get_step(src,node2_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
+	STANDARD_ATMOS_CHOOSE_NODE(1, node1_connect)
+	STANDARD_ATMOS_CHOOSE_NODE(2, node2_connect)
 
 	update_icon()
 	update_underlays()

code/ATMOSPHERICS/components/binary_devices/circulator.dm

@@ -9,6 +9,7 @@
 	icon = 'icons/obj/pipes.dmi'
 	icon_state = "circ-off"
 	anchored = 0
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 
 	var/kinetic_efficiency = 0.04 //combined kinetic and kinetic-to-electric efficiency
 	var/volume_ratio = 0.2

code/ATMOSPHERICS/components/binary_devices/dp_vent_pump.dm

@@ -24,6 +24,7 @@
 	idle_power_usage = 150		//internal circuitry, friction losses and stuff
 	power_rating = 7500			//7500 W ~ 10 HP
 
+	pipe_flags = PIPING_ALL_LAYER
 	connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_SUPPLY|CONNECT_TYPE_SCRUBBER //connects to regular, supply and scrubbers pipes
 
 	var/pump_direction = 1 //0 = siphoning, 1 = releasing

code/ATMOSPHERICS/components/binary_devices/passive_gate.dm

@@ -5,6 +5,8 @@
 /obj/machinery/atmospherics/binary/passive_gate
 	icon = 'icons/atmos/passive_gate.dmi'
 	icon_state = "map"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "passivegate"
 	level = 1
 
 	name = "pressure regulator"
@@ -257,8 +259,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 #undef REGULATE_NONE
 #undef REGULATE_INPUT

code/ATMOSPHERICS/components/binary_devices/pipeturbine.dm

@@ -139,6 +139,9 @@
 		src.set_dir(turn(src.dir, 90))
 
 //Goddamn copypaste from binary base class because atmospherics machinery API is not damn flexible
+	get_neighbor_nodes_for_init()
+		return list(node1, node2)
+
 	network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 		if(reference == node1)
 			network1 = new_network

code/ATMOSPHERICS/components/binary_devices/pump.dm

@@ -15,6 +15,8 @@ Thus, the two variables affect pump operation are set in New():
 /obj/machinery/atmospherics/binary/pump
 	icon = 'icons/atmos/pump.dmi'
 	icon_state = "map_off"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "pump"
 	level = 1
 
 	name = "gas pump"
@@ -236,5 +238,4 @@ Thus, the two variables affect pump operation are set in New():
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()

code/ATMOSPHERICS/components/binary_devices/volume_pump.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/binary/pump/high_power
 	icon = 'icons/atmos/volume_pump.dmi'
 	icon_state = "map_off"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "volumepump"
 	level = 1
 
 	name = "high power gas pump"