When deleting a repo, the package bits on the server aren't removed, even if they are orphaned. To delete them then requires a WS call per package, which will add up in the case of deleting, say, an RHEL base channel.

I suspect (just my gut feeling) that the typical behavior in deleting a repo would be to reclaim that space as well, so we should provide a hook on repo delete that will have the Pulp server clean up the package bits (assuming they aren't being used by another repo) as part of the repo delete. That'd make the API a single call in that case.

Implementation Notes:
- The repo API already has an option for "keep_files", though I'm not 100% sure it works. It's set by default to False but the files aren't being deleted.

- Once that's resolved, we need to update the repo WS API to accept this as an optional flag in the DELETE call (we already do something similar for CDS unregister as a reference).