Add support for Azure Copy Blob

Presently lacks support for CopyBlobOptions.  API reference:

http://msdn.microsoft.com/en-us/library/dd894037.aspx
@andrewgaul That syntax is a bit strange, and I know what your intent is here. Rather than using a `@RequestFilter`, what about just adding this simple header annotation? `@Headers(keys = COPY_SOURCE, values = "/{fromContainer}/{fromName}")``