Don't override state dump ict on restart.

Addresses #481
Made initial and final cycle time persist over multiple restarts.
Removed never-used dead_letter module.
Made simulation mode work with recent changes.
Merge pull request #482 from hjoliver/481.initial-cycle-time-var-on-restart

Don't override state dump ict on restart.
Merge pull request #490 from hjoliver/sim-mode-for-recent-changes

Sim mode for recent changes