Save drafts and then publish drafts on a set date

[MCNorthwood]

The earlier version of Piranha had the ability to save drafts and then publish it. From an already published page.
Essentially creating a replica of the page that can be edited without having to update right there and then. Having that added again would be a useful tool, especially with the new preview working as it is now and to save a draft of a published page and having the ability to view it in all screen sizes.

[tidyui]

Yes, this is a part of issue #289 which mean to handle both unpublished revisions and history revisions of previous versions. We started working on it for 5.3 but decided to postpone it for 6.0 as it will take a lot of work in the manager to really make the feature simple and intuitive.