TradHeli: Rate PID Improvement. Limit Integrator wind-up when PID output is saturated. Also a little bit of general clean-up for readability.
TradHeli: Change to throttle controller to allow swash plate collective to move, even if disarmed, if we are in Acro or Stab.  This is slightly dangerous... as a user could cause a problem if they do not follow the proper usage procedures.  If they do not route the ESC through the APM, but instead direct to Rx.  And then if they do not Arm, they could take off in Stab mode while disarmed, but then when they switch to Alt_Hold, it will drop the collective to the bottom and they will fall.  This can be saved by switching back to Stab.  And it requires operation outside of the normal operating procedure.

This change is being made because most heli users expect to be able to check the swash plate operation before arming and taking off.
TradHeli: Remove unused RSC Mode 3.
TradHeli: Creating motor_runup_complete bool which is to confirm that the heli motor is running. This will be used for advanced features in the future.
TradHeli: Fix Heli rate controller filter rates.
TradHeli: Creating new unified roll/pitch rate controller.
Copter: check set_mode for failure

Previously if set_mode failed it would return the copter to stabilize
mode.  With this commit set_mode returns a true/false indicating whether
it succeeded or not so the caller can make the decision as to the
appropriate response which could be to stay in the current flight mode
or try another flight mode.
Plane: move failsafe variables into a structure

this makes the logic a bit easier to follow
Plane: don't read control switch when ch3 is in failsafe

use ch3_counter not just the final flag
Plane: check the control switch a bit more often

faster response to mode changes
Plane: set mode CIRCLE on short failsafe in AUTO

this makes the code match the docs
AP_Math: added two new vector/matrix ops for kalman airspeed filter
AP_GPS: added velocity_vector() method
Plane: added note on type of airspeed in docs
AP_Airspeed: added auto-calibration support

This uses a Kalman filter to calculate the right ARSPD_RATIO at runtime

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
Plane: use new airspeed calibration code

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
Plane: update to new license boilerplate for GPLv3

we had LGPLv2 in some places, despite the fw being GPLv3
AP_Airspeed: added EAS2TAS in airspeed driver

this keeps the true airspeed ratio in the airspeed driver, which seems
the most logical place
AP_AHRS: added true airspeed support in AHRS

use true airspeed for wind calculations, and allow other drivers to
ask for the current ratio
AP_TECS: use ahrs EAS2TAS for true airspeed