Added exclude_page attribute that will keep the page out of sitemap
and page listings.

This is for creating pages that mimic older structure and contain
forward links, but that I want otherwise to be invisible.
Added a new post, as well as some static pages mimicing old (years
back) site structure, pointing to the blog post.

Also added exclude_page attribute for exlucing page from sitemaps etc.,
but not sure whether that will work in git pages at all. We'll see.