Bug 1055048: Move legal docs handling to separate app.

* Add generic view for legal docs.
* Convert privacy app to use new legal docs utils.
I feel like anything beyond the most basic customization of django's generic CBVs is better approached with functions instead. While this class isn't that long, the equivalent function(s) would be about as long without requiring the reader to trace through all of the complexity of `TemplateView`'s class hierarchy to fully understand it.