[ground_segment] add joystick hat to input2ivy

You can use the Hat<Position>(<hat_name>) function to trigger events,
where <Position> is one of
Centered/Up/Right/Down/Left/RightUp/RightDown/LeftUp/LeftDown

Only one hat can be used, but the interface will allow multiple ones in
the future.

closes #460
[nps] make radio_control type datalink work
[conf] update xbox and sidewinder joystick examples
[peripherals] mpu60x0_i2c: only copy ext data if i2c_bypass is false
[imu] fixes for imu_drotek_10dof_v2

- fix copying of unscaled gyro/accel data
- make i2c addresses of mpu and hmc configurable
- change orientation so z-axis is down when chips face up: define IMU_DROTEK_2_ORIENTATION_IC_UP
- silence some warnings
Merge branch 'master' of github.com:paparazzi/paparazzi