pointerc: support button events

pointerd: support button events

pointerd: exit cleanly on SIGINT

motion-control: signal: set SA_RESTART

gy-801-dump: signal: set SA_RESTART

motion-control: reduce yaw downscale

this make movements (subjectively?) more friendly in general case

sensors::L3G4200D: enable high-pass filter @0.05hz

this helps with fighting nearly-constant drift

ahrs: complementary: ignore yaw from tilt

math::quaternion: add from_euler

add controlling client for gy-801

add pointer controlling over udp

add README

math::quaternion: remove early test leftovers

ahrs: tilt: guard against acos(>1), acos(<-1)

ahrs: implement complementary filter

ahrs: tilt: fix direction

ahrs: implement tilt

gy-801-dump: bump gyro read rate

gy-801-dump: perform quaternion forward integration

gy-801-dump: continuous measuring