UX: switch dashboard to be the new dashboard

Also:
- add pageviews
- add problems and version sections

app/controllers/admin/dashboard_next_controller.rb

@@ -3,6 +3,7 @@ require 'disk_space'
 class Admin::DashboardNextController < Admin::AdminController
   def index
     dashboard_data = AdminDashboardNextData.fetch_cached_stats
+    dashboard_data.merge!(version_check: DiscourseUpdates.check_version.as_json) if SiteSetting.version_checks?
     dashboard_data[:disk_space] = DiskSpace.cached_stats
     render json: dashboard_data
   end