(DO NOT MERGE) initial experiment for enabling accordion control for lms navigation.

Initial changes to enabling the navigation accordion control, presuming no configuration or settings necessary to merge this into the platform for now. 

1.) IN PROGRESS - Expose collapsible navigation control
2.) Add in breadcrumb navigation above Unit page sequential allowing for clearer presence/location especially if user has navigation collapsed.
3.) When user clicks subsection in navigation sidebar, default (eventually) to collapsing sidebar once breadcrumb is in place. 
4.) Visual cleanup to existing sequential bar and iconography used for accordion controls.

https://www.dropbox.com/s/oihhfxcan6qwe3e/Screenshot%202014-03-07%2005.17.15.png

via Hackathon 6. https://github.com/edx/edx-platform/wiki/Hackathon-Six%3A-New-Digs