Allow for fully refreshing incremental dataflows

Dataflows can now be refreshed incrementally, which is great.

However, it is often required that perviously ingested data should be periodically updated, e.g. to accomodate retroactive changes. Right now, you don't have the option of fully refreshing a dataflow that has been set to incremental.

Also, yes, you can get into the incremental settings, toggle on and off and apply the changes and then the refresh will be full. But this is a dirty workaround and, ideally, this type of full refresh should be able to be scheduled periodically.