SPIKE: Investigate PublishHandler performance

[unclecheese]

The PublishHandler is quite inclusive -- fetching everything in the ownership structure and adding it to the snapshot as "WasPublished." This has a significant performance impact. A page with 10 blocks takes ~3000ms on SCP.

Thoughts:

• Is it necessary to include every single object, or can we get more creative with the query that marks the "Published" event in the UI?
• Consider using findOwned instead of getting the most recent ChangeSet? (Race condition!)