Some thoughts on dub housekeeping tasks for future design work

[rikki cattermole]

Dub isn't thread-safe. It would require significant structural changes 
to get any form of parallelism going on.

But the problem is that you have to retrieve metadata from the registry, 
pass that into getBestPackage and from there perform additional 
downloads. It is absolutely insane to have to do this when the logic is 
already compiled into dub-registry!