SkRasterPipeline: implement support for SkTableColorFilter

SkRasterPipeline: implement support for SkTableColorFilter

This adds and uses a byte_tables stage that converts to bytes, looks up
in the tables, then converts back to floats.

We treat this as color filter as pure math, not considering anything
colorspace related: no transfer functions, no gamut to change, etc.

Change-Id: If5fefc1bcef61a0fb0ae279002a0dd1547e429ea
Reviewed-on: https://skia-review.googlesource.com/7413
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>