[#85] Better selection of most recent 1.x version

- use version_compare on the keys to get the latest 1.x version.
[#85] manuals > 1.9, < 2.0 use "manual.html" as index page

- Added a rewrite rule to fix that, for when the sidebar is used to
  select a version from the "landing page" of any given manual page
[#85] Updated manual sidebar

- Use "current" as the option for a redirect
Merge branch 'hotfix/85' into develop