update the edit dialog to remove shortcuts conflicts
display shortcuts conflicts directly in the dialog.

shortcuteditdialog take 2 new optionnal arguments:
* conflictCallback: a function or methode that return a shortcut
conflict name.
* cbArgs: the optional arguments to pass to conflictCallback
add a _num attribute
comment lines that remove the Shift modifier

with its lines when a special character is pressed (é, è, ç), the
equivalent of a QWERTY keyboard is sent.
add "setShortcuts" method
replace "editAction" by "findShortcutConflict" and "removeShortcuts"
add the findShortcutConflict method