Use the super class type if we have it and there isn't one provided.

An isolated pull request. It's super handy for me, but I could see you not being thrilled with it. My data is being entered by hand in a spreadsheet by a non-engineer, so avoiding extra technical property entering when possible is a win.

This allows the simple case of a page that is contained in another page or tome (so the type is
known) to forgo explicitly providing the page type if it isn't using a subclass type.