Added PreviewLinkAutopopulate plugin to auto-populate preview links

[stephen-cox]

Part of localgovdrupal/localgov#600

[ekes]

Is there something else that needs to be done other than checking out the branch. I've got it, and done a site install, and used demo, but I don't see the button, only one to copy the preview link.

Also is it intentionally only getting the next level of child pages, or should it be getting all child pages (using the Nested Storage)?

[stephen-cox]

Also is it intentionally only getting the next level of child pages, or should it be getting all child pages (using the Nested Storage)?

I missed that subsite pages can also be parents along with overviews, I'll have to update to logic to handle this.

[finnlewis]

@stephen-cox working on this today