Allow modification of node title in *beforeEdit* callback

If the input value is changed in *edit* callback, the cursor ends up at the end of the text.

Being able to change the node title in *beforeEdit* avoids this.
Changing the input value in *edit* also breaks detection of modification.

My use case is, that I display more information, than should be editable, e.g.:

    Standard-Kettengehänge in Güteklasse 8 | 30* | (37) | [138]

for editing, only:

    Standard-Kettengehänge in Güteklasse 8 | 30*

should be available.