Add stack/deck mode for column

[ZabejAga]

Here is an idea:
in case 2+ windows in column be able to switch mode to deck (dwm, qtile) aka stack (i3) where the top (or last focused window) are visible at full height. Its better to have separate color/border thicknes for such deck/stack. Keyboard shortcut with arrow up/down should rise windows under top window.
useful for terminals, file managers, chat programs, ie arranged by type.

[YaLTeR]

Hey, I guess like in the existing discussion: #698

[ZabejAga]

looks like.
soryan )