ITranscriptLogger should support update and delete operations

[Jeffders]

trafficstars

As part of PII/IP filtering, clients and channels can request that activities be redacted. This influences the transcript logger and middleware the bot builder SDK supports. For example, Microsoft Teams is introducing this capability to send targeted messageUpdate and messageDelete operations to change and/or delete activities (for example, if a credit card number is passed, this really should not be saved, but often is missed by bot development).

To facilitate this, we need to augment the ITranscriptLogger interface, or extend it with ITranscriptRedactor or something that has update and delete operations.

[Jeffders]

Once this is done, we should also provide updates to samples that demonstrate this transcript logger and show how the delete and updates are used.

[stevengum]

Needs to be triaged and a parent issue created...