Improve Guise project mummy configuration with page section.
As discussed in GUISE-149, we need a separate subsection in the Guise Project mummy section for pages.
In particular we have mummy.pageNamesBare; this should be mummy.page.namesBare to be consistent with the image configuration in GUISE-149.
Sites need to be changed and the online documentation updated.
We probably should have a check for the legacy mummy.pageNamesBare and emit a warning (or even an error) if present. If we do that, a ticket should be opened to remove the check in a future version.