/status: add more information to /status page.

Add the following:

* Container name, machine name, worker id.
* Container uptime, puma uptime, worker uptime.
* Number of requests processed by current worker.
* ExifTool version.

Also change /status page to show information in tables instead of lists.

app/logical/danbooru/helpers.rb

@@ -0,0 +1,6 @@
+module Danbooru
+  module Helpers
+    module_function
+    extend ActionView::Helpers::DateHelper
+  end
+end