Returns an item containing a keystroke which matches KeyQueue and contains maximum amount of shortcuts.
IsHandled method looks through all Items and all keystrokes in this items to find a keystoke with a maximum amount of shortcuts. isHandled method returns item containing such a keystroke.
For example, if KeyQueue contains three shortcuts:"Esc+Esc+Esc" and Items property contains item with following keystrokes matching KeyQueue: "Esc", "Esc+Esc" and "Esc+Esc+Esc", IsHandled method returns item, containing "Esc+Esc+Esc" keystroke.
If no item with a keystroke matching KeyQueue found IsHandled method returns nil.