Default focus to contact list

If you start typing with the contact list focused, Dexter is smart enough to redirect your focus to the search bar. Since this is true, default focus should be on the contact list. This allows a couple of nice things:

1. We get the hint text displayed in the search bar when the application is opened
2. We get easier keyboard navigation since the focus is where it needs to be to use the arrow keys.

To make this experience complete, focus should also be given back to the contact list if the search bar becomes empty