JCLOUDS-458:Added Blobstore Abstraction

JCLOUDS-458:Added Blobstore Abstraction
Minor Changes testCopyUrl
Just a personal preference...handle the "exceptional case" in the if? I.e.
```
if (md5Hash == null) {
   return null;
}
HashCode hc = HashCode.fromBytes(BaseEncoding.base64().decode(md5Hash));
return hc;
```