Form builder: Add possibility to display archived forms and questions

[czosel]

In order to allow "unarchiving" things, there needs to be a way to find archived things in the first place. Maybe something like a "Show all forms" or "Show archived forms" link below the form list?

[fkm]

For forms this is relatively simple: Just add the possibility to show archived forms and link to the usual edit view.

Questions are a little more tricky, because there are two lists:

• List of questions inside form: Show archived questions as well (disabled/strikethrough) - this lets the user know that there is a question that could potentially be unlinked from the form.
• List of questions in the entire system (after clicking "+"): Don't show any archived questions (this is already the case)

In the future, when #47 is implemented, the "Archived" toggle should only be displayed on the "global question edit" view, and not on the "form-question edit" view.

[fkm]

First part is done #50