This lets you list your currently active profiles, as well as let you discover
new profiles, provided sparse.profile_directory is set.
Includes JSON output. Future revisions can build on this to provide richer
metadata (parsed from the profile files).
Should probably be repo.wvfs.join(profile_directory).
Actually, this whole thing should probably be operating on the manifest, so the user doesn't have to have these files materialized inorder to enable them.