Supporting publication-provenience relationships in cakePHP

This would require implementing the code to show related publications in proveniences page, and to show related proveniences page in publications page.

And for testing the sanity of cakePHP, I could try adding some dummy data after the code's done to check?

But for real data, we need to sort of identify the connections between publications and proveniences. Rune's project has little overlap with our publications (so I'm thinking maybe we append their pubs to our pubs?)