[#722] Hibiscus: adjust header

shrink the header image on mobile view to leave enough space for the
navigation links, etc
[#722] Nouveau Oleanders: tweak header on smaller screens

* only one of the big background images

* vertical navigation instead of horizontal

* no margin around the title/subtitles (the ones that "wrap" around the
  background image on bigger screens)
[#722] Stepping Stones: fix page title on smaller screens

It was being pushed to the right; that only needs to happen when we have
a sidebar
[#722] Add meta name="viewport" to core2

* instead of maximum-scale, which prevents zooming, use initial-scale

* remove mobility's Page::print becasue it now matches core2 exactly
[#724] Add "jump to modules" link to all Tabula Rasa children

* removes the jump to modules link from mobility, puts it into core2's
  Page::print

* in some cases, style to fit the header better

* adds a Page::print_header() function which prints the global title,
  global subtitle, page title, and module jump link. Some styles may not
  use this, especially if the header is arranged in a special manner
  (that's okay; this is more for convenience)