Implement linked contact menu option

Remove unlink option from QuickContact.
Link now appears when the contact has only one raw contact.
Otherwise a new "View linked contacts" menu option appears.
This dialog shows all linked contacts (including read-only) and
has buttons for adding another contact or unlinking all of them.
Show progress dialogs for each of these actions.

Test: Manually verified:
  * View linked contacts only appears when there are more than one
    raw contacts
  * Link appears otherwise
  * Pressing add goes to the contact picker and correctly joins the
    selected contact
  * Pressing unlink opens the confirmation dialog
  * Canceling or dismissing the confirmation closes everything
  * Unlinking from the confirmation does the unlink
  * Confirmed the above with rotating on each dialog and during the
    progress dialogs

Bug: 32707898
Change-Id: I39435a07fefce4276e34ba302001ff3dab352516