Distorted Android

Split up postprocessing into queue of effects + blit with depth.

Major speedup, BLUR fully optimized now.

Multiblur app, worst case (all 8 cubes blurred with max radius, HIGHEST quality: Nexus5X: 46.7 FPS, Nexus 4: 29.7 FPS.

Minor speedup.

Move on to Stencil on both stages of the BLUR + separate 'blit with depth'.

This works wonders on Nexus 5X ( r=50 quality=HIGHIEST 1,4,8 cubes: 59.3,43.6,41.0 FPS! ) but it somehow fails to clear the DEPTH and STENCIL buffers on Nexus 4....

Correct a bug where postprocessed objects would not re-appear after the app went briefly to the background.

Switch on Stencil in Postprocessing.

This is a clear win on Nexus 5X; on Nexus 4 it is debatable - faster on loads where area to be postprocessed is not much (~20% ?) of the screen; slower otherwise.

Move to a new way to detecting depth of postprocessing halos.
This switches off stenciling (hopefully temporarily!)

10% speedup with postprocessing.

Beginnings of support for multi-COLOR attachment Framebuffers.
This will be used in OutputSurface's Postprocessing Buffer.

Some improvements to DistortedRenderState.