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.
