Made Primitive.state private.
Default Primitive.vertexCacheOptimize to false.
Merge pull request #1267 from AnalyticalGraphicsInc/issue1239

Default Primitive.vertexCacheOptimize to false.
Merge pull request #1266 from AnalyticalGraphicsInc/issue1206

Made Primitive.state private.
Merge remote-tracking branch 'origin/master' into gltf