time-varying data support in OpenTimelineIO (originally: "Implement Curve Schema")

Implement curve schema for Bezier, linear, and others?

[See Appendix C of the FCPXML document, 2004](http://mirror.informatimago.com/next/developer.apple.com/documentation/AppleApplications/Conceptual/FinalCutPro_XML/FinalCutPro_XML.pdf) as an example implementation.

Start by reading the issue's linked FCPXML Appendix C reference and compare its example implementation with OpenTimelineIO's current schema concepts. Define what support for Bezier, linear, and other curves would require, then confirm the expected scope and completion criteria with the maintainers before identifying implementation and test locations.

Written by the indexing model from the issue text.