CHUI-326 FIXED (One entry per conversation with a user in conversation log...

CHUI-326 FIXED (One entry per conversation with a user in conversation log timestamped with most recent utterance/activity.)

- Modified LLConversationLog to show only one entry per conversation with user. I.e. there can't be two conversations with the same session_id in LLConversationLog.
- Got rid of processing voice sessions
- Refactored creation of conversation in LLConversationLog
- Refactored a little bit LLConversation and LLConversationLog: function names and made some functions private