Add shelves list to interior_ref_lists

So that shops can have multiple shelves that save their page, filter, sort, etc.
state to the server. Buttons for the shelves are reconstructed in the plugin
during the load shop procedure.

test_data/interior_ref_list.json

@@ -2602,5 +2602,23 @@
       "angle_z": 1.006,
       "scale": 1
     }
+  ],
+  "shelves": [
+    {
+      "shelf_type": 1,
+      "position_x": 1.001,
+      "position_y": 1.002,
+      "position_z": 1.003,
+      "angle_x": 1.004,
+      "angle_y": 1.005,
+      "angle_z": 1.006,
+      "scale": 1,
+      "page": 1,
+      "filter_form_type": null,
+      "filter_is_food": false,
+      "search": null,
+      "sort_on": null,
+      "sort_asc": true
+    }
   ]
 }