Improvement by not activating a random other client if the lowered client isn't active at all. Also applying this alteration to the shortcut variant (w/o altering the general behavior there)

Added clientUnderMouse() -used as well by nextFocusPrefesrMouse- and pass the focus there when lowered by mouseclick.
No idea whether it should apply to toggle as well (esp. not activating because of raising)

Yes - I hope nextFocusPrefersMouse remains working ;-)