Remove app.configure

We have long wanted to remove this code since any sort of configure logic is trivial to do at the app level. It also minimizes our use of magic env variables.

Besides the removal of app.configure, the other breaking change is `json spaces` off by default. If users want to pretty print json, there are plenty of awesome browser extensions or they can enable it in their app however they want.

I wish the view cache setting was also something we could stop using the env var for by default but that is a more serious breaking change. Maybe given that this is all for a 4.x target we could document it and require folks to set it themselves (which I believe to be the correct course of action).