Introduce the concept of draft content for all resources

[leandrocp]

Currently only pages and layouts allow users to edit a draft before publishing changes, and soon we'll have preview for pages. That gives the users a workflow to create and edit pages before they are ready for production.

Components and the other resources on the other hand are updated as soon as the changes are saved, which may cause unintended behavior if the content isn't ready to go live yet.

So we could introduce the same concept of draft and publish for the other resources and establish a pattern across all resources.