Accelerometer and Gyroscope support on mobile devices

[mulshine]

Accel and Gyro classes implemented for WebChucK to be used on mobile devices. Both modeled after HID,Accel
and Gyro interface with browser/JS "devicemotion" and "deviceorientation" events, respectively, and allow you to listen for and receive AccelMsg's or GyroMsg's inline with WebChucK code, providing x, y, z data in each case.

Gyro gy;
GyroMsg msg;

0 => int device;

// open gyro 
if( !gy.openGyro( device ) ) me.exit();
<<< "gyro '" + gy.name() + "' ready", "" >>>;

<<< "only on mobile" >>>;

// infinite event loop
while( true )
{
    // wait on gyro event
    gy => now;

    // get one or more messages
    while( gy.recv( msg ) )
    {
        // print gyro values
        <<< msg.getGyroX() + " " + msg.getGyroY() + " " + msg.getGyroZ() >>>;
    }
}

Big thanks to @terryzfeng for assistance in the architecture here!