crmMosaicoBlockMailing - Fix "Unsubscribe Group"

Upstream made some changes in how the list of groups is supplied (CRM-21411, circa
v4.7.28).  This patch ports the change from civicrm/civicrm-core#11258.

Note the use of `CRM.crmMailing.testGroupNames || CRM.crmMailing.groupNames` is intended to
provide compatibility with older and newer protocols.

ang/crmMosaico/BlockMailing.html

@@ -83,11 +83,13 @@
                 <select
                     class="form-control"
                     id="inputUnsubscribeGroup"
+                    crm-ui-select="{dropdownAutoWidth : true}"
                     name="baseGroup"
                     ng-model="mailing.recipients.groups.base[0]"
                     ng-required="true"
                 >
-                  <option ng-repeat="grp in crmMailingConst.groupNames | filter:{is_hidden:0} | orderBy:'title'"
+                  <option value=""></option>
+                  <option ng-repeat="grp in groupNames | filter:{is_hidden:0} | orderBy:'title'"
                           value="{{grp.id}}">{{grp.title}}</option>
                 </select>
               </div>

ang/crmMosaico/BlockMailing.js

@@ -1,5 +1,27 @@
 (function(angular, $, _) {
-  angular.module('crmMosaico').directive('crmMosaicoBlockMailing', function(crmMailingSimpleDirective) {
-    return crmMailingSimpleDirective('crmMosaicoBlockMailing', '~/crmMosaico/BlockMailing.html');
+  angular.module('crmMosaico').directive('crmMosaicoBlockMailing', function($q, crmMetadata, crmUiHelp) {
+    var directiveName = 'crmMosaicoBlockMailing', templateUrl = '~/crmMosaico/BlockMailing.html';
+    return {
+      scope: {
+        crmMailing: '@'
+      },
+      templateUrl: templateUrl,
+      link: function (scope, elm, attr) {
+        // Common elements - like crmMailingSimpleDirective
+        scope.$parent.$watch(attr.crmMailing, function(newValue){
+          scope.mailing = newValue;
+        });
+        scope.crmMailingConst = CRM.crmMailing;
+        scope.ts = CRM.ts(null);
+        scope.hs = crmUiHelp({file: 'CRM/Mailing/MailingUI'});
+        scope[directiveName] = attr[directiveName] ? scope.$parent.$eval(attr[directiveName]) : {};
+        $q.when(crmMetadata.getFields('Mailing'), function(fields) {
+          scope.mailingFields = fields;
+        });
+
+        // Unique elements
+        scope.groupNames = CRM.crmMailing.testGroupNames || CRM.crmMailing.groupNames;
+      }
+    };
   });
 })(angular, CRM.$, CRM._);