Markdown and other files in this repo use a lot of non TLS endpoints

[pjfanning]

Examples can be found quickly at:
https://github.com/search?q=repo%3Aapache%2Fwww-site%20http%3A%2F%2F&type=code

Ignore license text but URLs for doc pages and downloads should HTTPS where possible.

I have one PR for one page - #669

Ideally, a bigger changeset such be created.

[sebbASF]

Also, some references in XML and RDF etc may look like URLs, but they are not, e.g.

www-site/data/eccn/bisnotice.xsl

Line 3 in 6a38f61

xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

Such references must not he changed.