Bug 1021: OVRSBSRenderer*: Add texture filtering parameter (bilinear/none), adjust FBO texture params (alpha, filtering); Demo: Pass all parameters w/ arguments, use sane good defaults.

Turns out that using bilinear texture filtering w/o multisampling is 'good enough' ..

- OVRSBSRenderer*:
  - Add texture filtering parameter (bilinear/none)

  - Adjust FBO texture params (alpha, filtering)
    No alpha needed in FBO sink/target!

- Demo: Pass all parameters w/ arguments, use sane good defaults.