home: enable home bar app switching using swipe gestures

Allow users to switch the active app by swiping left or right on the home bar. Implements #68

This is working already! There was a problem when dragging the home bar up. The swipe feature caused the active application to be switched while dragging up in some cases. I think that is confusing, that's why I added a patch for it. But it could also be considered a feature by some people.

Potential improvements

• This could be implemented using a DragGesture instead of a SwipeGesture. That would require some way to make the applications fade in/out from the left/right, but it would probably be more pleasant to use.
• Add a minimum of required velocity to switch app. Could possibly improve the user experience.

I would love to hear about your opinions/suggestions/reviews!