Oculus Rift Improvements

- Now requires OVR SDK 0.2.5
- New chromatic aberration correction shader.  Can be disabled by
setting $pref::OculusVR::UseChromaticAberrationCorrection to false prior
to enabling Rift display (such as for screen shots).
- FXAA on by default when using full screen on the Rift.
- Can now manually override IPD from script.  Otherwise value set in
profile is used.
- Raw sensor data now available through input events (set
$OculusVR::GenerateSensorRawEvents to true) and console methods.  The
raw data is acceleration, angular velocity, and magnetometer reading.
- Can determine if magnetometer calibration data is available using a
console method in order to notify the user.
Merge pull request #497 from DavidWyand-GG/OculusRiftUpdate

Oculus Rift Improvements