Doc: Update online documentation template

This change brings the online template up to date with recent
changes:
    - Update links in header and footer.
    - To improve page load time and reduce load on qt.io,
      do not load images from the main site.
    - Fix auto-scroll/highlight jQuery to work on anchors
      containing full stop ('.') characters
    - Responsiveness: Fix menu issues with narrow views
    - Fix styling of subscript/superscript HTML tags
    - Make script URIs protocol-agnostic

Change-Id: I219e8ce6ff2e70f9374ad5e037ceda8f710a6a10
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>