Train page: make height of each stop rigid

[lucas42]

At the moment, as the time counts down for each stop, the width of the time varies.
This can cause the whole line to overflow dynamically and hence change the height of the stop.

By fixing the width of each time element, the height of each stop should stay constant. (It's fine that stops with longer names / more interchanges have more height, provided the height never changes just because of the countdown)