Auto-populate handbooks

that patch landed but we still don't create complex node types like book. we might want to wait until pwolanin's patch lands since boks are in flux.

This profile, at least for another few months, is only for 5.x anyway, so books aren't a moving target there...
That said, this is lower on my priority list, since personally, I mostly care about this profile for project* testing.

It looks like devel can create books, but not nodes that are child nodes of a book. There's an issue in the devel queue at #303143: Generate hierarchical books to add that functionality, however.

Getting this issue fixed might be helpful for people working on the d.o redesign.