0.5.2 state watcher for reconfigure

This branch contains the changes in 0.5.2_state_migration_tools which haven't been merged yet. The real set of changes are in the last commit https://github.com/dnephin/Tron/commit/201e447ffd5371a25269e6ee74c529c60fa4871c

This allows a user to change the state_persistence configs and tron will properly recreate the StateManager, and rebuild the state for the new config.