Add polyline loops.
Add Sandcastle example.
Add tests.
Update CHANGES.md.
Tweak CHANGES.md
Merge pull request #1521 from AnalyticalGraphicsInc/polylineLoop

Polyline Loop
Merge branch 'master' into materialUniforms

Conflicts:
	Apps/Sandcastle/gallery/Polylines.html
Update after merge.
Update CHANGES.md.