Mosaic reacts to "move focus" commands when one pane is maximized

[imsnif]

To reproduce:

• open 4 panes
• make the focused pane occupy the whole screen (at the time of writing this is done with ctrl+e)
• move focus (at the time of this writing this is done with ctrl+p)
• see that the mouse cursor moves to its location on the other panes that are not visible

This command should be blocked when there is a pane in full focus.

[imsnif]

@denismaxim0v is working on this (why can't I assign it to him?)