Add sonar data storage

js/data_storage.js

@@ -93,6 +93,7 @@ var SENSOR_DATA = {
     accelerometer: [0, 0, 0],
     magnetometer:  [0, 0, 0],
     altitude:      0,
+    sonar:         0,
     kinematics:    [0.0, 0.0, 0.0],
     debug:         [0, 0, 0, 0]
 };