Cloud Backup (BaaS) support

[tintoy]

Where practical, retain the semantics of the API as CloudControl provides it (rather than trying to provide an abstraction / application-level error handling as part of the client).

• Expose backup status on Server struct.

APIs:

• Backup service
  • Enable Backup for a Server
  • Disable Backup for a Server
  • Change Backup Service
• Backup clients
  • Get Backup Client Types
  • Add Backup Client
  • Remove Backup Client
  • Modify Backup Client
  • Cancel Jobs for Backup Client
• Policies
  • Get Storage Policies
  • Get Schedule Policies

Additionally:

• Unit tests
• Integration tests
• GoDoc comments