Disable unforked interval runs.

Clarify error message.

Move fork and interval logic to application (specs pending).

Clean code logic, fix specs.

Allow unforked client runs with daemonize or splay
Do interval and splay sleep before running client.
Reconfigure signal trapping.

Exit gracefully when sent TERM

Fix spec.
Update for removed unforked interval client runs.
Tidy up some comments, whitespace.
Fix wording, add updates for interval sleep first, signal processing