MWDK should warn users about invalid qset properties on creator save

[clpetersonucf]

MWDK is okay with arbitrary properties in a question object which Materia itself explicitly ignores and truncates from qsets before they're saved to the database. This has resulted in new widget developers creating invalid or incorrectly structured qsets because the MWDK doesn't inform them otherwise.

This should probably be bundled with additional preflight tasks like #43, #26, #21, and #7.