background worker stuff
fixed timetable crashing

perhaps if +someone+ would have remembered to clear the stackpanel
containing the old timetable before appending everything we wouldn't
have this problem
fixed buttons allowing crashing behaviour

*added property in ViewModel of TimeTablepage that always returns false.
Appbar arrows are then reenabled in codebehind once the BackgroundWorker
completes
fixed appbar button
fixed timetable view and select bus direction listbox style
merged with bgworker