Layouts can't be overridden on archive pages

[robneu]

Right now, the only archive that can be controlled is the author archive which has an option associated with the author's author meta data. All other archives can only use the "global" layout option, which probably isn't great on more complex sites.

I'm not sure how granular we need to get here, but having some type of control over the layout within archives would definitely be a good thing.