Per-contact note access

Provides per-contact access to view specific contact notes.

Once the extension is enabled, it will add a new "note privacy" setting for "Specific People", which then allows selecting a contact with a user account.

Note that unlike the default CiviCRM behaviour, when someone cannot see the notes, they will see a list of notes for which they do not have access and they will be able to see the subject (but obviously not the contents). This is to help in situations where staff might not know that a note exists, and therefore need who to contact if they need access.