Add support for Cloud DNS (fixes #216)
Add extension methods for calling IDnsService methods synchronously
Add the UpdateDomainsAsync operation
Add the UpdateRecordsAsync operation
Add the UpdatePtrRecordsAsync operation
Refactored DNS-specific data models to their own namespace
Represent unique identifiers with specific strong types
Added synchronous extensions for the recently added update operations
Improve efficiency (reduced system resource overhead) of DNS job polling