Prefer Notes (Notiz) Field of Datev Contacts as Display Name if it's not empty (CL-1880)

A datev contact can have multiple phone numbers (“Kommunikationen”). Currently, each of those numbers is imported with the same display name, making searching for the correct number cumbersome. A big improvement would be the following algorithm: If the “notiz” field of a phone number is not empty, use this as the display name, and move the current title into the “company” field.

See also the initial idea here.