Update question archive/visibility status via API
Before, we relied on a DeferredUpdate in SpecialHomepage::execute to make
changes to question records stored in the user's preference.
TransactionProfiler is not happy about this as it's a write on a GET.
- switches ApiQuestionStore to require a POST
- only loads the questions (without updating) on GET
- adds two POST requests at Homepage.js which will load and update questions