Remove 20 question maximum limit per category

[WesleyBranton]

Summary

Due to the API limitations, the add-on will only list up to 20 questions from each category. If the category has more than 20 questions, the oldest questions will not appear on the list.

It's possible to list more than 20 questions per category by calling the API again to request the second page of the questions and additional pages if there are more than 40 total questions in the category.

Motivation

This would ensure that old questions do no go unanswered, as they currently do not appear on the user's question list. It would also be a valid alternative to issue #153.

Potential drawbacks

This could dramatically increase the traffic to the SUMO API. It would also increase the time it takes to load questions, since the add-on would need to make the first API call, wait for a response, check if the list matches the 20 question maximum, make a new API query and repeat.