Add a vertical UI mode

[shenef]

Could be helpful with managing screen space.
This is different from #233 unless resizing the window reflows the contents.

A very rough mockup:

[Avasam]

I pretty much came to the same layout you did 👍

WIP: I still need to properly reflow the actions buttons (that's the the part that moves the most), everything else is nearly identical. This work also opens the door to full window resizing with PixMap scaling. Not sure when I'll have the time to finish it though.

Landscape	Portrait