Add support for Soft Deletes

[dkarlovi]

https://github.com/Azure/azure-storage-blob-php/blob/master/src/Blob/Models/BlobProperties.php

[brecht-vermeersch]

• Missing blob properties required for storages using soft-delete (deletedTime, remainingRetentionDays)
• Add blob undelete
• Add storage container undelete?

[brecht-vermeersch]

Improved tests to allow testing on storage accounts with soft delete enabled #19