Adaptor state phase 1

[jipperinbham]

This initial PR introduces a new SessionStore that can be configured in either the yaml or json. The first step here is to integrate the store into the Pipeline as well as make the Pipe responsible for setting the last Msg is passed along.

Currently, no adaptors implement this functionality because I feel like the semantics of the change may be adjusted once we start getting the adaptors integrated.

begins to address #33