Consistent stop icons for all route stops

- GlobalApplet::stopIcon returns the icon for given route stop flags.
- Always ask the model if a stop is currently highlighted or the home stop,
when checking the flags of a route stop item.
- Add route stop flags to journey stops and also use consistent stop icons there.
- The context menus of route stops now also use the icon shown for the stop
as icon for the menu title.
- Move highlighted stop information to the Info structure used by the departure
AND journey models. Also move the method to get flags for a route item in the
model to PublicTransportModel to be usable by both derivates DepartureModel
and JourneyModel.