FEATURE: advance search groups (#198)

Allow advance search filter to select topics assigned to specific group

assets/javascripts/discourse-assign/connectors/advanced-search-options-below/assigned-advanced-search.hbs

@@ -1,12 +1,14 @@
 <div class="control-group pull-left">
   <label class="control-label" for="search-assigned-to">{{i18n "search.advanced.assigned.label"}}</label>
   <div class="controls">
-    {{user-chooser
+    {{email-group-user-chooser
       value=searchedTerms.assigned
       onChange=(action "onChangeAssigned")
       options=(hash
         maximum=1
         excludeCurrentUser=false
+        includeGroups=true
+        assignableGroups=true
       )
     }}
   </div>