Number headers for site

Hi Rich,

This branch has changes related to numbering our headers.

I updated the number headers class we use for our current guides to be kicked off as a <java> Ant task instead of the custom task def that extends Ant's Task class ... its just easier to debug these classes when they have a main(). I then made a copy of it to use for the site's number headers class.

I committed some images that are in our  guide's images folder but must not have gotten checked into develop/learning-paths/images -- presumably they reside in folks local environments. I had to commit these as our check images task fails without them.

I added landing-page.markdown files for us to add content that introduce learning paths and each of the chapters/categories/sections which contain the indiv article markdown files for learning paths. We can add more contact to them later, but for now, when a user clicks Learning Paths, or one of the chapter links in the KB Article Nav, they'll land on some KB article based on these landing-page.markdown files. I tested this out locally with the learning path importer that I'm working on and it works well. :)

Nick did the heavy lifting of adapting the original number headers code to our site's directory structure.

You can test the dist target from learning-paths, to see this code in action.

Talk with you later.

Jim