Adding first pass stuff for replication.
Tested replication and it passes first attempts.
Fixed empty list error.
Added dump and restore.
Working and tested dump and restore with time bounds.
Added some minor sanity checks.
Finishing off replicator node.

 * Added to launch file
 * Added to README
 * made client time 24 hours
Switched default time to 24 hours ago rather than now, to allow easier use in scheduler.
Change action definition to use duration into the past.
Changed collections type to StringList to allow for datacentre comms to task schduler.
Merge pull request #49 from hawesie/hydro-devel

Added replication for message store