ar drone params: zero out pitch, roll rate_d terms
flight: factor maybe_float into its own module
flight: alt hold filter and estimator code factored into modules
flight.controller: rename thrust to altitude
flight.control.altitude: fill out more of controller
mavlink: regen smaccm-mavlink with AltCtlDebug message
Flight.Control.Pid: change application of iGain so dt scaling works

iGain effective when adding to the accumulator, not applying the accumulator
to the output, so that multiplying gains by DT before input to controller
is valid for a varying dt.

Won't effect any existing tuning since the I term in all of our controllers is zero
old althold is deprecated
replumb flight with new AltControl architecture

* AltControlDebug struct lives in Flight/Types, not in Control.AltHold,
  which fits our conventions
* ThrottleTracker moved to its own module, tested
* Parameters renamed, only use parameters we actually have
* Mavlink output uses new debug struct, new message
flight.control.pid has state variables storing intermediate p,d values for debugging
flight.params: fixed names for altitude params

* something's a little bit funny with group composition
Flight.Control.Altitude: controller works well at steady state and vz=0

Still need to add outer throttle controller (start with proportional to
stick with deadband, add absolute height controller afterwards), tune
better with nonzero inputs, tune for initial velocity not equal
to commanded velocity
flight.control.altitude: factor ThrustPID into its own module
px4ioar_params: remove deprecated throttle fields
flight.control.altitude: stub out throttle input interface & position pid

neither work yet
control.altitude: throttle input of rate basically works, but untuned

need to extend mavlink info so we can tune more effectively
regen smaccm-mavlink for latest ALT_CTL_DEBUG message
unify alt control debug flight type with mavlink message
flight.control.altitude: fix debugging, tune parameters

actually starting to fly pretty nicely.
flight.control.altitude: refactor estimator parameter