Add train option to wait until station be enabled

[Djekke]

TL;DR

Add options to trains: wait until next station in list goes online.

What ?

Another tab in train menu with settings for this train.
Add checkbox for this option

Why ?

It's will help to improve use of possibility to enable\disable station via circuit signals.
For example with this feature possbile to make easy wait stations between destinations.

Example

A -> B -> C
A - load smthg
B - wait station in middle
C - unload smthg, disable station when it has more then X items

Without this options train will go A <-> B, while C is disabled.
Or i need to wire signal from C to B to make wait condition, but it nigilate the possibility of station disabling.