BlobstoreService.get shall return List<String> instead of List<S3Object>

https://github.com/PredixDev/blobstore-samples/blob/master/blobstore-aws-sample/src/main/resources/templates/index.html

BlobstoreService.get returns List < S3Object > which means it is constructs the list of all S3Objects. This is unnecessary as finally only getKey method is used on those S3Objecs to list the names of the files. It is better to have:

        for (S3ObjectSummary objectSummary :
                objectList.getObjectSummaries()) {
            objs.add( objectSummary.getKey());
        } 

and we should later use those keys in the presentation layer.