Add switch to toggle alignment of the menu between left and right side of the window

[friwid]

I have my second screen on the right side. Having the menu on the right side of the window would make it easier for me to read the map, as the player icon would be nearer to my point of view and not further away, when the menu is open. It would be a "nice to have"-feature to be able to align the menu to the right side with a little switch. :)