Consider a Nebula option to automatically delete stored contact form after a period of time

[chrisblakley]

Will need to figure out what durations we would want to provide, and I would definitely want to add a bullet point to the diagnostic metabox as well and maybe even to the WP Dashboard metabox also.

May also want to add a hook to allow other plugins/themes to delete entries from other forms and things as well down the road.