[Wishlist] Add double clicking in addition to Shift, Ctrl, Alt, Windows modifiers of a QAP hotkey button

See BorisB post (#3)

2018-07-31 (JL): I did some work on it. It is possible to set mouse double-clicking as a trigger modifier. But this technique works and is easy to code in a standalone script when the hotkeys are saved inside the script itself. But it would be harder in QAP because it needs to save/retrieve the hotkeys selected by the user in the ini file.