Bulk API: Get back URI's

[sammefford]

It appears I'm not getting back the uris from bulk write requests. They should populate DocumentWriteOperation.getUri().

[sammefford]

We'll probably just make all bulk write methods return an array of DocumentDescriptor objects. Since this has been out since EA2 and we haven't had any feedback about this missing, we'll just make sure it's there for 8.0-1