`move-node-to-monitor` `right`/`down` should place the windows to the most left/up available position

[nikitabobko]

Given the following configuration:

    monitor1                   monitor2

    v_tiles                    h_tiles
      window1 (focused)          window2
                                 window3

(monitor2 is to the right of monitor1)

run move-node-to-monitor right

Expected:

monitor2
h_tiles
  window1
  window2
  window3

Actual:

monitor2
h_tiles
  window2
  window3
  window1

The reason: right now, move-node-to-monitor unconditionally places the window as the last child of the rootTilingContainer, but it should prefer to place the window as the first child in cases when the window is moved to the right or to the down

Note: as of #183, the move command will suffer from the same bug

[nikitabobko]

Fixed & released in 0.19.0-Beta