TranscriptLoggerMiddleware set turnContext.Activity.From.Role

[tracyboehrer]

Fixes #891

Also brought to parity with:

            // log incoming activity at beginning of turn
            if (turnContext.Activity != null)
            {
                turnContext.Activity.From ??= new ChannelAccount();

                if (string.IsNullOrEmpty((string)turnContext.Activity.From.Properties["role"]) && string.IsNullOrEmpty(turnContext.Activity.From.Role))
                {
                    turnContext.Activity.From.Role = RoleTypes.User;
                }

                // We should not log ContinueConversation events used by skills to initialize the middleware.
                if (!(turnContext.Activity.Type == ActivityTypes.Event && turnContext.Activity.Name == ActivityEventNames.ContinueConversation))
                {
                    LogActivity(transcript, CloneActivity(turnContext.Activity));
                }
            }