Three changes.

- Add FOR_EXPORT_ONLY to Data column.
- Make VCardComposer use Contacts instead of RawContacts.
- Make VCardComposer honor FOR_CONTACT_ONLY regardless of
  the intention of any caller, which makes composer unable to
  compose any contact with "is_restricted" flag, which is unseen
  from outside the contacts provider.

Internal Issue number: 2147248, 2143207