Navigate through search results using Alt+Up/Down

[ManuelSchneid3r]

This is common practice for "tabbing" though a vertical list. This would be awesome since I start a zeal seach using albert from keyboard. Initially the matchlist is focussed. When I click a result it loses focus and then I have to use the mouse to select another result.

[trollixx]

Just to clarify, the idea here is that Alt+Up/Down should always move selection up/down in the search results?

In this scenario another question comes up - when should we trigger loading of the new content? Since focus is not in the list widget, Enter wouldn't work. Perhaps, rely on Alt+Enter then...

[ManuelSchneid3r]

Yes always move and directly load content. Thats a convenient way to browse the results without the need to touch the mouse.

[trollixx]

This should play nicely with #749, since I do want to give an option to decide when a page should be loaded.

[trollixx]

Finally got to implementing this, please test!