[#2956] Refactoring the scopes entry

Hi guys!

See sha: b84f52c28d969b5143521261d818105824eaea5e for more information. Basically, now that the `request` scope problem is solved with the request_stack, the whole scopes entry is much much less important. I've updated it to use a make-believe example, which I think is pretty good, but creating custom scopes is quite rare.

So, I'm not convinced this entry still has a ton of value, but we've given people good warning at the top so that 99% of people will just solve their problem and move on. And for the 1% that does want to learn more, it's an interesting entry.

As usual, comments on any of my mistakes is appreciated.

Thanks!