When an EML doc is waiting to be indexed, show a message in the Editor

[laurenwalker]

When I try to open an EML document in the Editor that has not yet been indexed, I get a Not Found error. But it is more accurate to say that the document is still processing.

The reason why we need to wait on the indexing to complete is because there is no other way to find out which resource map aggregates an EML other than the Solr discovery index. We need to parse the resource map for the Editor to work.

When Solr return 0 numFound, we should send a request to the system metadata API and if the object exists, display a "processing" message.