FEATURE: Configure Admin Account

Adds a "Step 0" to the wizard if the site has no admin accounts where
the user is prompted to finish setting up their admin account from the
list of acceptable email addresses.

Once confirmed, the wizard begins.

lib/homepage_constraint.rb

@@ -4,6 +4,8 @@ class HomePageConstraint
   end
 
   def matches?(request)
+    return @filter == 'finish_installation' if SiteSetting.has_login_hint?
+
     provider = Discourse.current_user_provider.new(request.env)
     homepage = provider.current_user ? SiteSetting.homepage : SiteSetting.anonymous_homepage
     homepage == @filter