Update sidebar navigator to use accordion menu.

[lc3tutor]

I want to organize the page navigation in the side bar to use an accordion menu. There will be grouped pages in the future and the idea is to make it easier for the user to navigate pages and keep the sidebar length to a minimum. The side bar should match the style of the website and the accordion should open to the section that contains the current page.

Acceptance:

• Navigation bar allows iterating through the pages
• Navigation bar allows two levels of sections top->sub->subsub section and subsection. We can add a third level at a later time.
• Navigation will make sure the appropriate sections are expanded for the current page and that those panels are highlighted

[lc3tutor]

Additionally, this menu should be upkept in a manner that is easy to update in the future. I am thinking that there is a config file that is the source of truth for the website directory.