Rename GrSamplerState to GrEffectStage.

R=robertphillips@google.com
Review URL: https://codereview.appspot.com/6777053

git-svn-id: http://skia.googlecode.com/svn/trunk@6135 2bbb7eff-a529-9590-31e7-b0007b416f81
38 files changed