site-generator: Added all the modules that the script and the templates use to make it explicit what is required. templates/shared-utils.tpl.html: Added a new TT² macro called 'absolute_url' which takes two arguments, the base and the path or relative URL. It's fairly primitive but seems to work. templates/content-about.tpl.html, templates/content-recording.tpl.html, templates/content-request_a_slot.tpl.html, templates/content-requested_topics.tpl.html, templates/page.tpl.html: All calls to 'absolute_url' changed to use two arguments, and the link definitions adjusted to match this change.