Remove constant "No suitable device found." log message when no GPS f…

…ound.

Debug only now.

Call `gracefulShutdown()` before reboot.

Fixes cyoung#717.

Link against math lib for lowpower_uat.go.

Change ForeFlight support note in README.

Change CircleCI to test to build master.

Clean up cputemp.

Merge pull request cyoung#657 from cyoung/ahrs_dev

Sync master with ahrs_dev (minor webui changes).

Merge pull request cyoung#641 from cyoung/ahrs_dev

AHRS for v1.4r1.

Ensure SensorQuaternion synced with IMUMapping.

Merge remote-tracking branch 'origin/master' into ahrs_dev

# Conflicts:
#	Makefile
#	main/equations.go
#	main/gen_gdl90.go