Use epsilon value to compare duplicate polyline positions.
Add tests.
Update CHANGES.md.
Adjust epsilon value when comparing polyline vertices forduplicates.
GeoJSON loading performance improvements

1. Allow `ConstantProperty` to optionally return a reference for complex types rather than always cloning.
2. Have `GeoJsonDataSource` use a canvas object for `BillboardGraphics.image` instead of calling `toDataURL` on it.
3. Modify `Billboard.image` property to use the `id` property when a canvas element is assigned.
4. Have `PinBuilder` create a unique id for each pin canvas.
Allow ConstantProperty to be used with HTML elements.

Normally `ConstantProperty` requires `clone` and `equal` functions
for non basic types, but since `HTMLElement` instances support
reference equality; that's not needed in this case.
Update comments and CHANGES

Also fixed deprecated parameter used in viewerDragDropMixin.
Merge remote-tracking branch 'origin/master' into geojson-load-performance

Conflicts:
	CHANGES.md
Merge remote-tracking branch 'origin/master' into geojson-load-performance

Conflicts:
	CHANGES.md
Add relative tolerance tests to Math and Cartesian*.
Use relative tolerance test to remove duplicate positions from polylines.
Update PolylineGeometry and PolylinePipeline tests.
Add tests for equalsEpsilonRelative functions of Math and Cartesian*.
Fix combining multiple geometries that both have and have not been split by the IDL. Also, fix the quick bounding sphere reject when splitting by the IDL.
Updates from review.
Fixed endianess of VertexNormal extension size.
Delimit extensions with a hyphen in the accept header.
Merge remote-tracking branch 'origin/master' into geojson-load-performance

Conflicts:
	CHANGES.md
Changes after review.

Remove use of canvas.id from `Billboard`, but still allow it for `BillboardVisualizer`
Merge remote-tracking branch 'agi/master' into quantizedMeshExtensionsFix