storage.json 2016-01-01 Usage_List does not flatten

[jianghaolu]

In storage.json 2016-01-01, the Usage_List method remove the following from the 2015-06-15 spec:

        "x-ms-pageable": {
          "nextLinkName": null
        }

Which makes the method return UsageListResult instead of List<Usage>. This seems like an unnecessary breaking change in every language.

[lmazuel]

@amarzavery @devigned ?
Makes Python ugly too:

for usage in storage_client.usage.list().value:
    print('\t{}'.format(usage.name.value))