[Docs] Fix up the Help navigation and page

 * Site navigation menu should have consistent behavior and bring you to
   pages, rather than triggering PDF downloads. Remove sub-menu items
   and just have a simple page providing the relevant links to both HTML
   and PDF docs.
 * Update external wiki link from the old dellcloudedge Github
   organization to crowbar. Also add warning that external wiki contains
   information for a different version.
 * Remove unused code that generates (incomplete) HTML docs.
 * Remove outdated, Dell specific PDF docs.
 * Add symlinks to SUSE Cloud PDF documentation. Requires the
   susecloud-{admin,deployment,user}_en-pdf RPMs to be installed.
 * Add symlinks to SUSE Cloud HTML documentation. Requires the
   susecloud-manuals_en RPM to be installed.