Add database changing log as a new channel

[Oceania2018]

Add a new channel as the trigger entry.
Currently we have several different channels to trigger AI Agent to work on user request.
It will be nice if the agent can be trigger by database data changes.

The initial trial can be implemented for mysql-replica. we can add new new plugin like BotSharp.Plugin.ChangeDataCapture, and add IChangeDataCaptureHook to allow other plugin work with the changed data.