Add support for some ARDrone 2 specific sensors.

Navdata no longer publishes when there is no one listening.

msg/Navdata2.msg

@@ -0,0 +1,67 @@
+Header header
+
+# Navdata including the ARDrone 2 specifica sensors
+# (magnetometer, barometer)
+
+# 0 means no battery, 100 means full battery
+float32 batteryPercent
+
+# 0: Unknown, 1: Init, 2: Landed, 3: Flying, 4: Hovering, 5: Test
+# 6: Taking off, 7: Goto Fix Point, 8: Landing, 9: Looping
+# Note: 3,7 seems to discriminate type of flying (isFly = 3 | 7)
+uint32 state
+
+int32 magX
+int32 magY
+int32 magZ
+
+# pressure sensor
+int32 pressure
+
+# apparently, there was a temperature sensor added as well.
+int32 temp
+
+# wind sensing...
+float32 wind_speed
+float32 wind_angle
+float32 wind_comp_angle
+
+# left/right tilt in degrees (rotation about the X axis)
+float32 rotX
+
+# forward/backward tilt in degrees (rotation about the Y axis)
+float32 rotY
+
+# orientation in degrees (rotation about the Z axis)
+float32 rotZ
+
+# estimated altitude (cm)
+int32 altd
+
+# linear velocity (mm/sec)
+float32 vx
+
+# linear velocity (mm/sec)
+float32 vy
+
+# linear velocity (mm/sec)
+float32 vz
+
+#linear accelerations (unit: g)
+float32 ax
+float32 ay
+float32 az
+
+#Tags in Vision Detectoion
+uint32 tags_count
+uint32[] tags_type
+uint32[] tags_xc
+uint32[] tags_yc
+uint32[] tags_width
+uint32[] tags_height
+float32[] tags_orientation
+float32[] tags_distance
+
+#time stamp
+float32 tm
+