Implement smoothing filter for accelerometer data.
Run rotated gravity vector through smoothing filter to match phase with filtered accelerometer data.
Disable accel smoothing during init/arming so it does not interfere
Take magnitude of filtered gravity vector into account.
Move accel filter to separate function, for cleaner code and easier filter alteration.
Optimize for filter disabled case (AccelTau = 0.0).
Spelling of Spectrum to Spektrum
GCS Config: Crashing for an unknown board seems a bit harsh.
Added support for Mode 3 and Mode 4 to the TX Configuration Wizard. Fixed a number of bugs and issues in the wizard. Made some changes to wizard text and layouts as well.
pios_jedec: fixed usage of uninitialized memory

When reading the jedec device id the code only transfered one byte via spi leaving
the expected input buffer uninitialized. This may lead to the problem that flash
initialization fails because the expected input may be whatever the stack was set
when entering the function. The impact of the bug is somewhat limited tough as the
initialization usually takes place before starting up the rtos and thus is pretty
deterministic. So if the code passed init while testing it should pass init in
production as well.
Removed a spurious call to AccelsSet() that was causing garbage data to be transiently written to the Accels UAVO. Props to cyr for kicking off the discussion that led to the discovery of this bug.
Update HISTORY.txt with last releases info
GCS vehicle config: do not reset existing camera/accessory mixers [OP-691]

Still no fix for helicopter config (some code refactoring is desired).
Coding style fixes
Clarify comment about gravity vector
Change default AccelTau value to zero (filter disabled)
Take the magnitude of the correct gravity vector
GCS vehicle config: use better function name for readability [OP-691]
Merge remote-tracking branch 'origin/cyr/accel_filter' into rel-12.10.2
OP-716 Added checkbox to enable accelerator filtering (cyr fix)
OP-716 Added default TauAccel == 0.15 to wizard.