Add option to specify data update policy on view queries

[ecton]

The default behavior is to ensure the view is up-to-date before returning any data.

Keep this behavior by default, but add the ability to:

• Return stale data (don't wait for the view to update, pull whatever it can immediately with as little delay as possible)
• Same as above, except kick off a view update job to run in the background.

This allows ultimate flexibility: If you want eventually-consistent data accesss, use "update_after". If you know another process is updating the view regularly, you can just request stale data always allowing the other process to control the "caching".