#211, #183, #98: get the ability to copy/clone item.
Simply configure the parameter "copy" with the key of your choice and use
this key before/when dragging to toggle the copy behaviour.

Available keys are: space, enter, tab, esc/escape, backspace/back, shift/
maj, ctrl/control, alt, left/leftArrow, up/upArrow, right/rightArrow, down/
downArrow, ins/insert, del/delete, home, end, pgUp/pageUp, pgDown/pageDown,
F1-F12, and any number/letter of the keyboard (except for the keypad
numbers).
Simply use the special key string or the letter/number (in any case) in the
"copy" parameter and you're good to go.
Update the "lockX/lockY" parameters to bind a key used to lock axis

You can now use "true/false" to enable/disable permanently the axis lock,
or a special key string (see below) or a single letter/number. The axis
will then be locked while the corresponding key is pressed.

Available keys are: space, enter, tab, esc/escape, backspace/back, shift/
maj, ctrl/control, alt, left/leftArrow, up/upArrow, right/rightArrow, down/
downArrow, ins/insert, del/delete, home, end, pgUp/pageUp, pgDown/pageDown,
F1-F12, and any number/letter of the keyboard (except for the keypad
numbers).
Fire an event the dragging has been cancelled
Fix the cancellation of the drag
Redisplay the hidden element when the drag has been cancelled
Add a "cancel" parameter to configure the key used to cancel a drag

Use any special key string (see below) or a single letter/number.

Available keys are: space, enter, tab, esc/escape, backspace/back, shift/
maj, ctrl/control, alt, left/leftArrow, up/upArrow, right/rightArrow, down/
downArrow, ins/insert, del/delete, home, end, pgUp/pageUp, pgDown/pageDown,
F1-F12, and any number/letter of the keyboard (except for the keypad
numbers).