Add a reaction that restricts view access

[mjordan]

We have reaction that restricts view access based on the user's IP address, but we should have a reaction that restricts access that is decoupled from any specific type of "condition". This would allow us to use arbitrary conditions to restrict access.

We should retain the current restrict by user's IP address reaction because of the logic around redirecting to a proxy page.

It would be useful to provide conditions that may leverage this such as object state and date created.

[mjordan]

... and this must apply to datastream view access as well.