Add subcommand to push to Canvas

[dbosk]

We can add a subcommand that can push an exam to Canvas. Or maybe it's better to leave such features to canvaslms. Maybe just export to QTI format, or text2qti format.

But with Canas support we can extract the statistics afterwards too.

[dbosk]

If we have such a command in canvaslms we can import it here as a subcommand.