Package blobstore is a PLACEHOLDER for the blobstore implementation.
It's not currently implemented, but it may be implemented in the future, if someone decides they needs it (and they don't just use Google Cloud Storage directly).
They Key type here is provided simply for rawdatastore to correctly interface with BlobKey's written by other appengine apps (e.g. python).
Key is a key for a blobstore blob.
Blobstore is NOT YET supported by gae, but may be supported later. Its inclusion here is so that the RawDatastore can interact (and round-trip) correctly with other datastore API implementations.