359: discussions answerKey assessmentType

- includes moving the masterTopicId from the Journal and SharedWritingQuestion config to the answerKey
- initial simple handling of discussions assessmentType in the LocalAnswerMan

Jira: BRIX-359
359: new Discussion Mananager for getting topic posts and comments

- IDiscussionMan interface w/ types
- LocalDiscussionMan - The local discussion manager helps test locally as well as defines the structure of the information expected to be returned from the IPS.
- SubmitManager support for routing event requests to its discussion manager and returning the response

Jira: BRIX-359