[KNIFE-361] Delete underlying VHD blog image from Azure Storage by default when deleting Virtual Machine

https://tickets.opscode.com/browse/KNIFE-361

Delete VHD image by default, user option to preserve.

This enhancement reveals a design flaw in the current REST client implementation code - it uses an old version of the Azure Management API.

Several features that this plugin will need to support (Cloud Service Public Endpoint ACL configuration as an example) will require using more recent versions of the Azure Management API.