Implement 'reminders' section in `cloudsite-db.json`

[zanerock]

Overview

Sometimes we need to come back to things. Specifically, when creating a site, we can't activate the cost allocation tags right away. We have to give AWS time to discover the tags and make them available for activation. To deal with this, we want to add a reminders field to cloudsite-db.json. Each entry will consist of a type, id, description, and createdTime. The type determines a "reasonable waiting period". The id is the type (like 'billing-setup' folowed by a number which is currently, but not historically unique. E.g., 'billing-setup-1'.

Deliverables

• [ ] Whenever a user invokes a commaand, we'll check if there are any reminders which are past their reasonable waiting period, and if so, display the description and recommended action (using the 'reminders' command) to the user unless --no-reminders/-R is set.
• [ ] Implement --no-reminders/-R
• [ ] Implement cloudsite reminders do XXX [YYY...] where XXX is the reminder ID. This calls the proper handlers, e.g., update some-domain.com --do-billing; you can specify
• [ ] Implement cloudsite reminders do-all
• [ ] Implement cloudsite reminders list

[zanerock]

Work for this issue will begin begin on branch work-liquid-labs/cloudsite/95.