Produce aggregate views/sets

[mblayman]

Problem: Some users (like myself) might like to be able to view a set of wiki pages simultaneously. This could prevent lots of clicking around for pages that are viewed often. Eventually, a set could be selected to produce custom documentation (rather than freezing an entire wiki).

Solution: Add a set model to the tool that will hold references to other wiki pages. Since sets have little value as something anonymous, find a clean way to integrate it with authenticated users.