Configure trains to wait in the train stop until all (or some specific) layers are loaded.#2294

For example: Wait until 1 and/or 2 and/or 3 layers are loaded. My suggestion is to make a global setting for all trains as a menu with toggles for each layer at which to wait for loading. I also propose to make such a menu for each train stop, which will have a higher priority than the global setting. This will help in more flexible configuration of trains.

Haven’t made it to logic yet, but perhaps using wires fully block train until full, other wise train stopper works as it does?

Coming with 0.1.0