[libcontacts] Prefer organization name to contact details in display label

If a contact has no name details, but has an organization detail
including the name field, then it probably represents that organization
directly.  Prefer to use this detail as the display label in
preference to the contactable details of the contact.
Merge pull request #82 from matthewvogt/organization-name

[libcontacts] Prefer organization name to contact details in display label