LuaATC add trainparts(train_id)

Returns a copy of the trainparts table to allow tracking individual wagon ids
Also fixed a couple of file permissions from previous commits

advtrains_luaautomation/README.md

@@ -93,6 +93,9 @@ Removes any pending interrupts of this node.
 Make this active component send a digiline message on the specified channel.
 Not available in init code.
 
+ - `trainparts(train_id)`
+	returns a table with the ids of the cars the train is composed of, or false if `train_id` is invalid. `train_id` can be replaced with `atc_id` when used in LuaATC Rails.
+
  - `atc_send_to_train(<train_id>, <atc_command>)`
 	Sends the specified ATC command to the train specified by its train id. This happens regardless of where the train is in the world, and can be used to remote-control trains. Returns true on success. If the train ID does not exist, returns false and does nothing. See [atc_command.txt](../atc_command.txt) for the ATC command syntax.
 

advtrains_luaautomation/environment.lua

@@ -153,6 +153,12 @@ local static_env = {
 		local pos=atlatc.pcnaming.resolve_pos(parpos, "interrupt_pos")
 		atlatc.interrupt.add(0, pos, {type="ext_int", ext_int=true, message=imesg})
 	end,
+	train_parts = function(train_id)
+		if not train_id then return false end
+		local train = advtrains.trains[train_id]
+		if not train then return false end
+		return table.copy(train.trainparts or {})
+	end,
 	-- sends an atc command to train regardless of where it is in the world
 	atc_send_to_train = function(train_id, command)
 		assertt(command, "string")