Adapter warning/error reporting

[jminor]

Adapters should be able to report warnings and errors to the caller in a clear way.

[jminor]

This would be handy for cases like the ignore_timecode_mismatch flag on the EDL adapter. You don't just want to ignore problems, nor do you want them printed to the console.

Ideally you could provide a callback or handler that can accept warning messages, or progress notifications, and choose to stop or continue on each one.

[jminor]

There are several places where we raise ValueError and TypeError exceptions, which should really be custom sublcasses of OTIOError so the caller can distinguish OTIO-related issues with just coding errors.

[meshula]

flagging for TSC review, is there work to do here, or has the concern been addressed?

[reinecke]

The exception-based error reporting mechanism paired with controls via adapter args to fudge certain data is the way we'd like to proceed with this.