Previous version most of the time just got "stuck" on floating windows,
switching back and forth between floating window and tiled window underneath.
This was because "magic point" was left in the same position and thus next
navigation commands selected the same windows over and over again.
Now the "magic point" is moved around such that it doesn't overlap with the previously selected window,
and there are more complicated rules to make navigation between floating and tiled windows more natural.
The original behavior of navigating between tiled windows is preserved almost precisely.
Previous version also prevented switching windows using focusUp/focusDown
when in Full layout. Now there's a special case that handles such situations.
