Fix sampled packets with no defined epoch.

Fixes #1112 and a related regression for non-position sampled data.
Merge pull request #1113 from AnalyticalGraphicsInc/issue1112

Fix sampled packets with no defined epoch.
Rename CLAMP to CLAMP_TO_EDGE
Merge pull request #1118 from AnalyticalGraphicsInc/clamp

Rename CLAMP to CLAMP_TO_EDGE
Make extent and polygon primitives synchronous by default.
Merge pull request #1122 from AnalyticalGraphicsInc/syncPrimitives

Make Primitives synchronous.
Preemptively add a potential future file to .gitignore
Merge remote-tracking branch 'origin/master' into gltf