Move barometric pressure models to a new module.
Generate code to initialize the Kalman filter.
Move Kalman filter Ivory types to a new module.

This way I don't have to re-run the Template Haskell bits most of the
time.
Generate code to renormalize quaternion states.
Codegen tests for on-ground were exactly backwards.
Handle pressure measurements with noise in pressure-space.
Force C filter to process bogus-looking measurements.

The filter isn't working correctly yet, so most measurements look bogus.
Add a POSIX/C test driver for the Kalman filter.
smaccm-ins: remove package upper dependencies.
ivory-bsp-stm32: Refactor GPIO TH pin-generation.
Merge branch 'master' of github.com:GaloisInc/smaccmpilot-stm32f4
Fix typo of -Werror as "-Werrror".
smaccm-ins: Update for ivory-backend-c artifacts.
Provide a HasAtan2 Double instance with the class definition.
Move model noise parameters into the test drivers.

This way each user of the generic IMU sensor fusion model can have
different sensor noise parameters.
Add test driver for Paul Riseborough's test inputs.

This doesn't yet get remotely similar answers to Paul's though.
Fix orientation update equation.

1) The division by 2 was leftover from an earlier approximation.
2) Quaternion multiply is not commutative and was in the wrong order.
Factor SerializeRef instances out of Mavlink implementation.
smaccm-ins: Replace Matrix.L with ZipList.
Replace my matrix/vector/quaternions with ekmett's.