s3 restore: allow specification of Tier parameter

[martin3000]

Currently, in key.py the RestoreBody is built as

<?xml version="1.0" encoding="UTF-8"?>
      <RestoreRequest xmlns="http://s3.amazonaws.com/doc/2006-03-01">
        <Days>%s</Days>
      </RestoreRequest>

But amazon also allows a Tier parameter. With this, you can specify how fast the restore ist done:

<RestoreRequest>
   <Days>2</Days> 
   <GlacierJobParameters>
     <Tier>Bulk</Tier>
   </GlacierJobParameters> 
</RestoreRequest> 

When restoring an archived object (or using a select request), you can specify one of the following data access tier options in the Tier element of the request body:

Expedited - Expedited retrievals allow you to quickly access your data stored in the GLACIER storage class when occasional urgent requests for a subset of archives are required. For all but the largest archived objects (250 MB+), data accessed using Expedited retrievals are typically made available within 1–5 minutes. Provisioned capacity ensures that retrieval capacity for Expedited retrievals is available when you need it. Expedited retrievals and provisioned capacity are not available for the DEEP_ARCHIVE storage class.

Standard - Standard retrievals allow you to access any of your archived objects within several hours. This is the default option for the GLACIER and DEEP_ARCHIVE retrieval requests that do not specify the retrieval option. Standard retrievals typically complete within 3-5 hours from the GLACIER storage class and typically complete within 12 hours from the DEEP_ARCHIVE storage class.

Bulk - Bulk retrievals are Amazon S3 Glacier’s lowest-cost retrieval option, enabling you to retrieve large amounts, even petabytes, of data inexpensively in a day. Bulk retrievals typically complete within 5-12 hours from the GLACIER storage class and typically complete within 48 hours from the DEEP_ARCHIVE storage class.