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.
ivory-bsp-stm32: Refactor GPIO TH pin-generation.
Merge branch 'master' of github.com:GaloisInc/smaccmpilot-stm32f4