Add a menu item to quickly remove passwords from notes

[CampelloManuel]

It is not clear how passwords should be removed from notes. As of now, the user must:

1. open a locked note
2. type the password to unlock it
3. copy the text onto a new note
4. the new note will be unlocked and equivalent to the old note

The idea is to add a menu item called "remove password from note", which is different from the "unlock" button we already have. This one would set the note as not locked and stop asking for the password in the first place.