Expose is_opt_out contact property for Edit/Display in Profile and for Display-only in Contact View

Users need to be able to update civicrm_contact.is_opt_out via a web interface, and CiviCRM users need to be able to see if this condition is true.

1. Allow this property to be exposed in Profile forms by updating Contact.xml (add import=true). [This will also allow import of this property.]

1.1 When this property is set TRUE via Profile form submit (or Import), we ultimately need to invoke the same function that is invoked when this happens via email. (I see that there is an unsub_from_domain() function in CRM/Mailing/Event/BAO/Unsubscribe.php - but not sure if there is some higher level function which in turn invokes this??). Bottom line is that the results should be the same whether this state is updated via email or profie form submit - with the exception that the "method" property for the resulting civicrm_subscription_history record should be 'Web'.

2. If is_opt_out = TRUE, add the following string to the Privacy section of Communications Preferences fieldset: "NO BULK EMAIL (Opted-out)" [NOTE: Open to other suggestions for wording for this state :-) ]