Admin improvements

[djm]

We had an unexpected CSP-related outage due to an addition of a new rule, and the admin was not as helpful as it could be in an emergency. I would suggest the following changes.

1. The "Rules" admin does not showcase when the rules were created. Doing so would have given us the ability to see which new ones were added and thus find the problematic ones fast. Looking at the models this will require a new field(s) as there are no db-timestamp fields present.

2. The "Rules" admin should be sorted by the time they were created, so new rules appear at the top. This would have aided in resolution time.

3. When you have many "Rules", finding the one you're after over multiple pages in the Django admin is tricky. We should enable searching, so that searching for a certain hostname would find rules related to that hostname.