Add support for Azure Copy Blob

Presently lacks support for CopyBlobOptions.  API reference:

http://msdn.microsoft.com/en-us/library/dd894037.aspx
What if you instead use `@PathParam` instead of `@HeaderParam` on the `from*` args?
```java
@Named("CopyBlob")
@PUT
@Path("{toContainer}/{toName}")
@Headers(keys = AzureStorageHeaders.COPY_SOURCE, values = "/{fromContainer}/{fromName}")
ListenableFuture<Void> copyBlob(
      @PathParam("fromContainer") @ParamValidators(ContainerNameValidator.class) String fromContainer,
      @PathParam("fromName") String fromName,
      @PathParam("toContainer") @ParamValidators(ContainerNameValidator.class) String toContainer,
      @PathParam("toName") String toName,
      Optional<CopyBlobOptions> options);
```