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
- loads the questions as they are stored in the prefs (without checking for updated status, or writing any updates) on GET
- adds two POST requests at Homepage.js which will load and update questions
Because loadAndUpdateQuestions() takes about ~150ms on a homepage with six
questions, and isRevisionVisible() accounts for ~60ms, I opted to not do any
checks on the initial GET.