Remove unnecessary include disqus.
Remove sample page for tooltips.
Remove support for unused datatable.
Remove support for page.simple_map and page.complex_map
If the page contains the variable "sidebaractiveurl" in the yaml
frontmatter, this is additionally used to select the active item
in the sidebar. Useful, if the page doesn't have its own item,
but wants to activate e.g. the parent page.
