JCLOUDS-458:Added Blobstore Abstraction

JCLOUDS-458:Added Blobstore Abstraction
Minor Changes testCopyUrl
Better to use `BaseEncoding.lowerCase` and store this directly as a `HashCode`:

```
HashCode md5 = HashCode.fromBytes(BaseEncoding.base16().lowerCase().decode(httpStreamMD5));
```