add pool category search option

app/views/pools/_search.html.erb

@@ -28,6 +28,15 @@
         </td>
       </tr>
 
+      <tr>
+        <th><label for="search_category">Category</th>
+        <td>
+          <div class="input">
+            <%= select "search", "category", [["Series", "series"], ["Collection", "collection"]], :selected => params[:search][:category] %>
+          </div>
+        </td>
+      </tr>
+
       <tr>
         <th><label for="search_sort">Order</th>
         <td>