Queue source component when curating described.sourceLocation

If a curator supplies the sourceLocation for a package, then we should be able to use that information to queue the source for the package. That requires the crawler to either

* be given this info up front
* be able to call out to the service to get the definition for the component in question

Consider also the idea of requeuing a package if a curation changing the source location is merged. This might actually be the best way to trigger the flow.