Extrapolate the next set of poses for HMD and hand controllers.
Currently we predict 44ms into the future, this seems too high, however
it was discovered by inspection to be the best value.
Obviously there is a source of latency that we need to track down,
however even with this latency, it is a much improved experience.
Pass a InputCalibrationData to each inputPlugin and inputDevice.
This contains the most up sensorToWorldMatrix, avatarMat and hmdSensorMatrix.
Each input plugin can use this data to transform it's poses into Avatar space
before sending it up the chain.
This fixes a bug in the handControllerGrab.js script that relied on the hand controller
rotation/positions being in the avatar frame.
* Call vr::VR_Shutdown() when ref-count goes to zero. The ref-count
is ncessary because the vr::IVRSystem poitner is shared between the
the openvr input and display plugins.
* OpenVR plugins options will display in the menu if vr::VR_IsHmdPresent() is true.
This is faster then initializing all of openvr and less likely to conflict with the
oculus display plugin.
