Add road numbers to wagon properties, bordcom

A road number is used to allow users to set their own wagon numbers
other than the internal IDs assigned by advtrains. A railway company
would typically keep a roster of what rollingstock it has in road
numbers.

The road number can be set on the wagon properties formspec. It is
displayed above the wagon's inventory icon in the onboard computer as a
button, which will then open the wagon properties on that wagon.

Road numbers might be displayable as additional text entities on the
wagon like signs.

Currently opening the wagon properties (and sometimes onboard computer)
formspecs can be quite unreliable (at least on windows), so I hope that
closing the wagon 'main menu' before opening other formspecs helps that
reliability. It seems to be an upstream bug.

advtrains/wagons.lua

@@ -778,6 +778,7 @@ function wagon:show_wagon_properties(pname)
 	local data = advtrains.wagons[self.id]
 	local form="size[5,5]"
 	form = form .. "field[0.5,1;4,1;whitelist;Allow these players to access your wagon:;"..(data.whitelist or "").."]"
+	form = form .. "field[0.5,2;4,1;roadnumber;Wagon road number:;"..(data.roadnumber or "").."]"
 	--seat groups access lists were here
 	form=form.."button_exit[0.5,3;4,1;save;"..attrans("Save wagon properties").."]"
 	minetest.show_formspec(pname, "advtrains_prop_"..self.id, form)
@@ -810,21 +811,23 @@ function wagon:show_bordcom(pname)
 	form=form.."field[7.5,3.25;3,1;routingcode;"..attrans("Routingcode")..";"..(minetest.formspec_escape(train.routingcode or "")).."]"
 	--row 5 : train overview and autocoupling
 	if train.velocity==0 then
-		form=form.."label[0.5,4.5;Train overview /coupling control:]"
+		form=form.."label[0.5,4;Train overview /coupling control:]"
 		linhei=5
 		local pre_own, pre_wl, owns_any = nil, nil, minetest.check_player_privs(pname, "train_admin")
 		for i, tpid in ipairs(train.trainparts) do
 			local ent = advtrains.wagons[tpid]
 			if ent then
+				local roadnumber = ent.roadnumber or ""
+				form = form .. string.format("button[%d,%d;%d,%d;%s;%s]", i, linhei, 1, 0.2, "wgprp"..i, roadnumber)
 				local ename = ent.type
-				form = form .. "item_image["..i..","..linhei..";1,1;"..ename.."]"
+				form = form .. "item_image["..i..","..(linhei+0.5)..";1,1;"..ename.."]"
 				if i~=1 then
 					if checklock(pname, ent.owner, pre_own, ent.whitelist, pre_wl) then
-						form = form .. "image_button["..(i-0.5)..","..(linhei+1)..";1,1;advtrains_discouple.png;dcpl_"..i..";]"
+						form = form .. "image_button["..(i-0.5)..","..(linhei+1.5)..";1,1;advtrains_discouple.png;dcpl_"..i..";]"
 					end
 				end
 				if i == data.pos_in_trainparts then
-					form = form .. "box["..(i-0.1)..","..(linhei-0.1)..";1,1;green]"
+					form = form .. "box["..(i-0.1)..","..(linhei+0.4)..";1,1;green]"
 				end
 				pre_own = ent.owner
 				pre_wl = ent.whitelist
@@ -916,6 +919,13 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 	for i, tpid in ipairs(train.trainparts) do
 		if fields["dcpl_"..i] then
 			advtrains.safe_decouple_wagon(tpid, pname)
+		elseif fields["wgprp"..i] then
+			for _,wagon in pairs(minetest.luaentities) do
+				if wagon.is_wagon and wagon.initialized and wagon.id==tpid then
+					wagon:show_wagon_properties(pname)
+					return
+				end
+			end
 		end
 	end
 	--check cpl_eid_front and _back of train
@@ -1000,6 +1010,9 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 				if fields.whitelist then
 					data.whitelist = fields.whitelist
 				end
+				if fields.roadnumber then
+					data.roadnumber = fields.roadnumber
+				end
 			end
 		end
 		uid=string.match(formname, "^advtrains_bordcom_(.+)$")
@@ -1040,12 +1053,15 @@ function wagon:seating_from_key_helper(pname, fields, no)
 		end
 	end
 	if fields.inv and self.has_inventory and self.get_inventory_formspec then
+		minetest.close_formspec(pname, "advtrains_seating_"..self.id)
 		minetest.show_formspec(player:get_player_name(), "advtrains_inv_"..self.id, self:get_inventory_formspec(player:get_player_name(), make_inv_name(self.id)))
 	end
 	if fields.prop and data.owner==pname then
+		minetest.close_formspec(pname, "advtrains_seating_"..self.id)
 		self:show_wagon_properties(pname)
 	end
 	if fields.bordcom and self.seat_groups[sgr].driving_ctrl_access and advtrains.check_driving_couple_protection(pname, data.owner, data.whitelist) then
+		minetest.close_formspec(pname, "advtrains_seating_"..self.id)
 		self:show_bordcom(pname)
 	end
 	if fields.dcwarn then