Improve experience when discovering identity key error on send

New experience in the Message Detail view when outgoing identity key
errors happen, matching the Android View.

'View' button is only shown on outgoing key errors right now.

When a contact with an outgoing identity key error is clicked, they are
taken to a view like the popup that comes up on Android: an explanation
of what happened and three options: 'Show Safety Number', 'Send Anyway',
and 'Cancel'

Contacts are now sorted alphabetically, with the set of contacts with
errors coming before the rest.

FREEBIE

js/models/conversations.js

@@ -202,6 +202,14 @@
             }.bind(this)));
         }
     },
+    setTrusted: function() {
+        if (!this.isPrivate()) {
+            throw new Error('You cannot set a group conversation as trusted. ' +
+                            'You must set individual contacts as trusted.');
+        }
+
+        return textsecure.storage.protocol.setApproval(this.id, true);
+    },
     isUntrusted: function() {
         if (this.isPrivate()) {
             return textsecure.storage.protocol.isUntrusted(this.id);