Fixed saving Meal exposures

According to:
https://stackoverflow.com/questions/34328735/imageable-type-is-not-setting-for-polymorphic-associations
and
https://stackoverflow.com/questions/2494452/rails-polymorphic-association-with-multiple-associations-on-the-same-model

app/views/meals/_options.html.erb

@@ -9,7 +9,7 @@
         <tr>
           <td style="width:100%"></td>
           <td><%= select_tag 'quantity_id',
-            toggle_exposure_options(@project.meal_exposures, :diet) %></td>
+            toggle_exposure_options(@project.meal_quantities, :diet) %></td>
           <td><%= submit_tag l(:button_add) %></td>
         </tr>
       </table>

app/views/meals/toggle_exposure.js.erb

@@ -0,0 +1 @@
+$('#meals').html('<%= j render partial: 'meals/index' %>');