Restore tiled windows

Fixes #68 (closed) When a window is tiled to a position (top, bottom, left, right or max) then hitting a tile short-cut again untiles it and restores it back to the original size and location.

I have left the interaction such that if you tile left, then tile right short cut, it doesn't directly tile right, but first restores, then you need to hit shortcut a second time.

I debated having it tile right with just one short-cut. That can be done, but will require storing the tiled state in the window to avoid consuming restore. Let me know what you think.