Name already in use

Force alpha to 1 after FXAA

FXAA stores luma info in alpha, when rendering to a RT used as a texture
in UI it messes up everything.

Fog fixes

New temporal filter for DoF

Tweaks

Avoid GC allocate in ColorGrading GetCurveTexture

This is a workaround for issue #896121 https://goo.gl/MgKqu6

Changed to resample CoC values inside the chromatic aberration loop when CA is
enabled.

This commit includes major improvements to the temporal filter for DoF. See the
following document for details on the improvements.

https://goo.gl/3Rpxcz

This commit also includes changes to the other components.

**Changes to the TAA component**

- Added `jitterVector` property to share the current jitter vector with DoF.

**Changes to the Uber shader**

- Changed to use a full-resolution CoC buffer to blend DoF results in the Uber
  pass. This is needed to eliminate seams and aliasing caused by integration
  with TAA. This also improves the quality even when TAA is disabled.

**Changes to Common.cginc**

- Added `SEPARATE_TEXTURE_SAMPLER` macro that controls how MainTex is to be
  declared (sampler2D or separate texture/sampler).

The following is a brief list of the changes on the DoF component.

- Implemented a temporal reprojection filter for the CoC history buffer. It's a
  simplified variant of the TAA filter and tailored to have nearly-identical
  characteristics with a less cost.

- Changed to use R8 render textures for storing CoC values instead of RHalf.
  This is needed to compensate performance loss due to increase of the memory
  and bandwidth usage.

- Optimized with using the texture gather functions on Shader Model 5.

- Optimized the post blur filter. The sample count was reduced from 9 to 4
  without losing quality.

Uber shader checks debug variant first.