New per-pixel Phong code is enabled by setting `perPixel` parameter in Phong material.

This version is able to light single untesselated quad correctly.

Also it doesn't have point lights number limitation caused by varyings, all lights pass just through uniforms.

Performance wise it seems surprisingly quite similar to old version (stress test is ~6 fps faster with new version, though I guess for different use cases / GPUs it can differ).