SimulatedSensors: remove commented code
Autotune: remove RelayRate tuning mode

Previously an axis could be either tuned by RelayRate mode or
RelayAttitude mode. However, in practice only attitude mode was
changed. This removes the code that was never really utilized as
well as the unused mode.
Ground/Autotune: bring back the save button

This allows enabling the module. Not sure how it got dropped.
Autotune: removing RelayTuningSettings UAVO, no longer used

Also removing the unused code related to it. This included the
code related to saving the settings, although that was also
out of date.
Autotune: rename RelayTuning to SystemIdent

It is no longer using a relay tuning approach so
the name was not appropriate.
GCS/Autotune: use SystemIdent object now

This replaced the RelayTuning object
GCS/Autotune: update the description text and default sliders

Now using defaults of damping 1.1 and noise sensitivity 1.0.
The text also suggests values for more aggressive and smoother
flight.
GCS/Autotune: increase damping for outer loop gain

Previously this was 1.0. It produced outer Kp values
around 6-10. While these are definitely fliable they
are higher than people prefer. Increasing damping to
1.3 which will decrease the outer Kp to about 60%
of previous.
GCS/Autotune: validate the estimated system properties

When applying the computed settings, the autotune checks that
the response speed and gains are within reasonable limits. If
not, a dialog is presented informing the user and asking if
they want to proceed.
GCS/Autotune: UI cleanup and fixes
Autotune: save system identification properties

Now if you run the whole sequence (stops shaking at 90 seconds),
land, disarm, then the results of the system identification
process will be saved.

This allows actually applying the changes later, or trying different
slider values for different flights.
Autotune: only use 60 seconds
GCS/Autotune: improve instructions for new code