Add DBaaS engine Kafka

[dwilsondo]

Adds Kafka as a DBaaS engine.

Extends the following methods to accept Kafka specific user settings:

• GetUser
• ListUsers
• CreateUser

Adds Kafka Responses:

• ResetUserAuth
• ListOptions (see: GetDatabaseOptions)

Adds support for Topic management:

• ListTopics
• CreateTopic
• GetTopic
• UpdateTopic
• DeleteTopic

[andrewsomething]

Mostly looks great, but I did have a few questions inline.

Also, from the API responses, it looks like there are some new additions to the DatabaseConnection object that are not included here. I'm seeing:

      "application_ports": {
        "certificate": 25071,
        "sasl": 25080
      }

[andrewsomething]

👍 LGTM!