Add Plugin Mapper

[Reisen]

A Conduit Mapper needs to exist that will recieve and modify Messages passing through the conduit stream. A major issue to think about it was to do if a Message comes through that is a command which needs to be dispatched to another program in the cluster.

Potentially this means Message objects that pass through the conduit need to be wrapped in an Envelope so that we can simply change an incoming Message containing a block of commands into a cluster of Message instances that run individual commands, but with an Envelope type that can be used to piece together the end results later on.