Book keeping and file handling: Replica output data should be written to/read from a "replica sandbox"

[SrinivasMushnoori]

Currently we are using a convoluted mechanism for bookkeeping between replicas.
Having the Exchange Task determine EX pairs are creating a "renamed" soft link going from replica N output --> replica K input (assuming N and K have accepted to exchange). This eliminates the need to use PST names to refer to replicas as well as network communication agent and client.