Support for ttl & tts

[asilvas]

Global option, as well as per-config item rules. This would allow configuration to be "fresh" for options we expect could change over time.

[gshively11]

This could be useful for the yaml config if you decide to edit it outside of your app's normal CICD pipeline. If you use the Etcd source (still in progress), config will be automatically updated as soon as you change the values in Etcd.