Add logic to handle cancelled departures

[braintimeException]

Hi,

I have added the logic to handle cancelled departures.

A departure can have a property cancelled set to true. Unfortunately, this property is not always present, but it is mentioned in the example response here https://github.com/public-transport/hafas-client/blob/5/docs/departures.md, and I have seen it a couple of times myself as well.

The changes introduce a cancelled property to the Departure class and updates the UI such that the cancelled departures appear struck-through by default and can be configured not to be shown entirely.

[braintimeException]

should fix #9