Extract out site logic to a separate repository

[aplowman]

It would be better to have a separate repository for a blank wiki. This way other research groups could, in principle, use the wiki we have developed for their own purposes. This would also help us to distinguish commits that are content from commits that are site functionality. To make this work, I believe we would just add the "blank" wiki repository as a remote source to the "real" wiki; we could then periodically sync from the "blank" to the "real" wiki if any functional changes are made.