Conversation log

MSCWeb depends on another feature, i.e. conversation log that I had implemented and that too has not been accepted yet. This pull request is a part of a series of requests that have to be in place before I push MSCWeb implemented in coi-services. Unless of course you would rather want everything at once, which will actually make it difficult for you to review what it is exactly that is being merged.

Note that when I push the pyon portion of conversation log it too will be safe in the sense that it does not start unless indicated in the pyon.yml