Add DASHBOARD_PAGE_SIZE to settings

Add DASHBOARD_PAGE_SIZE to TEMPLATE.env and app.json

Parse dashboard page size value

app.json

@@ -127,6 +127,11 @@
       "description": "Custom location url to link to in frontend.",
       "value": "https://www.openstreetmap.org/?mlat=$LATITUDE&mlon=$LONGITUDE",
       "required": false
+    },
+    "DASHBOARD_PAGE_SIZE": {
+      "description": "How many services should be displayed on dashboard page?",
+      "value": "5",
+      "required": false
     }
   }
 }