atc_reset(): Removed unused string parameter and also clear ATC autocouple flag (Cpl)

Fixes H#189 and H#190

advtrains/atc.lua

@@ -93,6 +93,7 @@ function atc.train_reset_command(train, keep_tarvel)
 	train.atc_delay=nil
 	train.atc_brake_target=nil
 	train.atc_wait_finish=nil
+	train.atc_wait_autocouple=nil
 	train.atc_arrow=nil
 	if not keep_tarvel then
 		train.tarvelocity=nil

advtrains_luaautomation/atc_rail.lua

@@ -130,9 +130,8 @@ function r.fire_event(pos, evtdata, appr_internal)
 		get_rc = function()
 			return train.routingcode
 		end,
-		atc_reset = function(cmd)
+		atc_reset = function()
 			if not train_id then return false end
-			assertt(cmd, "string")
 			advtrains.atc.train_reset_command(train)
 			return true
 		end,