add great expectations quality object

[SimonAuger]

I would need this to fix the linter command when the quality object is great-expectations otherwise I encounter "data.quality.type must be one of ['SodaCL', 'montecarlo', 'custom'"] error with the linting and export command

[jochenchrist]

Thanks for your contribution! Decided to merge in current version, as this is not a breaking change.