Briefings for timetable mode

Activities have briefing text which can be seen in Menu.exe and also in-game in the F1 Help Window. This blueprints adds a similar text for each timetable and the Player Train which the user chooses within the timetable.

The text is taken from the timetable-or file and indicated by a "#briefing" marker. As newlines are not allowed in timetable-or files, "<br>" may be used to indicate a newline.

Discussion: http://http://www.elvastower.com/forums/index.php?/topic/33443-timetable-briefings/
Roadmap: https://trello.com/c/WpDk1Rrx/438-briefings-for-timetable-mode