Add tools field to package_tkj_balanduino_index.json

The missing tools field causes Arduino IDE 1.6.11 to not start if the Balanduino boards package was installed in a previous version of the Arduino IDE. If you attempt to install the Balanduino boards package using Boards Manager in Arduino IDE 1.6.11 it fails with a java.lang.NullPointerException error.

Author: per1234

package_tkj_balanduino_index.json

@@ -37,7 +37,8 @@
             }
           ]
         }
-      ]
+      ],
+      "tools": []
     }
   ]
-}
+}