Broken Links Throughout Site

I ran a link checker against the Sling Site as I was curious regarding some of the issues reported regarding broken links. The report returned a number of links being broken due to invalid markdown.

Certain links use references, even though they are to external pages. This results in a blank URL. Additionally, there are links to resources which no longer exist.

I resolved the issues as well as:

• Fixing broken links to the nabble mailing list
• Some minor spelling fixes
• Removed an unnecessary, broken link to localhost:8080 (should these be removed in general?)