#802: DB2 did not drop triggers on clean

Trivial implementation.
I don't use Flyway's clean() functionality, so I suppose leaving inactive triggers/tables/etc around could be ok, depending on your intended use. If you want to run migrate(), clean(), then migrate() again, I could imagine this causing errors if not done in a dependency aware order. Though, I buy that this is a bigger change than what you intended, and may be fine for most use cases. Documentation for the clean() method may want to address the possible limitation. 

In regards to using the ADMIN_DROP_SCHEMA command, I have found that to be quite delicate - Once you get a failure, you seem to have to manually clean out errorschema.errortable before you can run it again. That may no longer be an issue with a more modern version of DB2 however.