Dolphin "Point" simulation

[MichaelJW]

@catcallofcthulu asked in #7:

Would it be possible to use the VR software's built in pointer and send it to dolphin as mouse input?

Ideally I would like to rely solely on Dolphin's Motion Input tab, and not use the Motion Simulation tab at all, but currently there are real limitations with this, partly because Dolphin does not currently offer a way to specify IR data, and partly because I'm not syncing the accel/gyro simulation with the input refresh rate Dolphin uses.

The Point simulation has the particular negative consequence of disabling "tilt" input from the gyroscope, but the trade-off for that is the great increase in pointer accuracy it brings, so it's worth offering the option of binding Point to the coordinates where a ray cast from the IMU or XRController intersects with the screen.