[joystick] Added Logitech Extreme 3D Pro joystick
Start of work on Redundant Link. This first step modifies the exisitng link agent to allow it to be given an id (through the -link_id flag) and to send ivy messages of a different format (when -redlink is set). The messages are sent within the TELEMETRY_MESSAGE message as a  ;sv (colon-seperated-value) which are listed to by the link_combiner.py agent.
Started the second step of the redundant communication link, writing the Link Combiner agent. This agent receives ivy messages from the link agent(s) when they have a name specified, removes duplicate messages, then sends ivy messages of the same format that the link agent used to send messages.
Added GUI in GCS for multiple links. The information for this is sent from link_combiner.py in the LINK_STATUS message. The GCS now has a page in the notebook named Link, the ratio of active links appears in the main link indicator, and messages when a link is lost or gained are displayed in the console.
Adding support for displaying link status information when multiple aircraft are connected through the same link. Also added support for recording link status information in flight logs and displaying it during a replay.
Added sample redundant communications session to control_panel.xml.
[rotorcraft] Add stabilization attitude passthrough

This is usefull for the ardrone-sdk version which runs next to the ArdroneLib API program that controls the aircraft so that stabilization is allready done
[guidance] use atan2f instead of INT32_ATAN for more accurate route reference
[boards] fix LED_12 on Lisa/M 2
[stm32] sys_tick_handler declared in c file only
[rotorcraft] remove global waypoints_float
[rotorcraft] navigation_carrot calulation in separate function
[ins] rename estimator_z to ins_alt to avoid confusion with old stuff
[fixedwing] ins_alt_float: hopefully fix baro altitude
[fixedwing] ins_alt_float fixes/updates

- correct sign for altitude from baro pressure
- set initial altitude to ground_alt
- also update altitude after baro update
- make GPS_DT defineable in airframe file
[dox] fix comment about initial value of adaptive hover thrust estimation
[modules] baro_ets: BARO_ETS_TELEMETRY not only in SITL
[ahrs] float_cmpl: more precise warning
[modules] baro_ets: fix for SITL
fixedwing energy_ctrl

rate limiter with GS protect
rate limiter now in m/s/s (AIRSPEED_SETPOINT_SLEW)
fix in init