Define ManagedZone CRD and controller

[maleck13]

What

Define the managed zone CRD. We should keep this very simple for the time being. The spec currently likely only needs the root domain for the zone.
The status will need ready conditions, and a place to report nameservers back to the requester so that they can update their own DNS Provider to point at ours.
We may also want to record additional information in the spec/status such which provider this Zone is hosted in and the number of records currently assigned to the zone

Done

• Simple API Resource that specifies a root domain for a new zone to be used by the tenant e.g. apps.mycompany.com
• New Managed Zone controller within the traffic controller
• The new zone is assigned to a provider by the traffic controller
  (only 1 provider at this stage)
• The zone is then created in a provider via the traffic controller using provider credentials
• The zone status is updated with the nameservers for this new zone and a ready condition
• Unit tests in place