Update to Beta-4

-Adds support for multiple myos, tested with up to 3. Use blueprint
events for multiple myos as input mapping uses only primary myo.
-Added xArmDirection to myo device data
-Fixed PIE spam caused by stopping and resuming after a long duration;
the hub will be destroyed between sessions.
-Added preliminary support for calibrated values. Call
MyoCalibrateArmOrientation(int32 myoId) when arm is facing the screen,
after which all arm and body values are calibrated, some values are not
fully correct at this stage, use with care.