Anki add-on: Add note id

This adds a uuid to an empty field named "Note ID" when opening the add or edit note window. When the “Note ID” field is the first field, this automatically satisfies the rule that the first field has to be unique. That means the “real” fields with interesting content don’t have to be unique. (Personally, for synonyms i like to have the same content in the “Expression” or “Meaning” fields, and then put further information in note or disambiguation fields.) The note id field is also useful when editing the data outside of Anki (text export, edit, text import). With the add-on, Anki can reliably match the notes on reimport, even when the first "interesting" field changed. There is also a menu item that goes through the collection and fills all fields called "Note ID" with uuids. This menu item can be hidden (More links at the manual page. Also, the manual is out of date right now. Meh. This whole Anki add-on stuff is low priority for me.)