Add a selector for "Original-only" dandisets (along with draft-only and empty)

[yarikoptic]

As we will eventually get more of "derived" dandisets (as composition or containing derived data) it would be useful to be able to subselect them.

[satra]

@yarikoptic - i think this may require a few components:

• blob timestamp in relation to asset creation time
• provenance in asset metadata (this is why having search + copy functionality in the service would be better than the gist i wrote).
• eventually derivatives of data and not just copy of data (perhaps through services like dendro).

[yarikoptic]

I thought to base it on some entry in dandiset metadata which would establish relationship isDerivedFrom from other dandisets and then we consider that one derived. On per asset level would be too tough probably