Add simple searchable column support for non-AJAX grids

idk maybe even AJAX grids can use?  not gonna try at the moment

tailbone/templates/grids/buefy.mako

@@ -187,6 +187,9 @@
             <b-table-column field="${column['field']}"
                             label="${column['label']}"
                             :sortable="${json.dumps(column['sortable'])}"
+                            % if grid.is_searchable(column['field']):
+                            searchable
+                            % endif
                             :visible="${json.dumps(column['visible'])}">
               % if grid.is_linked(column['field']):
                   <a :href="props.row._action_url_view" v-html="props.row.${column['field']}"></a>
@@ -217,7 +220,7 @@
         % endif
       </template>
 
-      <template slot="empty">
+      <template #empty>
         <section class="section">
           <div class="content has-text-grey has-text-centered">
             <p>