Remove SkLightingShader and associated classes

Change-Id: I8050414c30dfdb5df23ca79955adc5ba3a29d3f5
Reviewed-on: https://skia-review.googlesource.com/31140
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
24 files changed