Security fix: no more matricola moving

We used to pass also 'matricola' every time we edit info. 
Now 'matricola' is the login name and can't be modified via API.
Do you mean that the matricola is present on disk because we allowed it earlier? If so, I suggest to automatically remove the matricola from all files on disk, rather than adding ad-hoc hacks for cleansing the object model opportunistically.