Question List Mode implementation

This uses tabulated-list-mode to build the list of questions.
The actual content of questions is displayed on a separate buffer using org-mode (for now of course, this is not permanent).
As intended, but that's a good point about the `require` business. We shouldn't make API calls like that unless the user asks for them. Something like `(stack-initialize)` should be created to initialize all of these variables. I'll make an issue for that.