* update templates and code references
* also a display_name property that defaults to cleaned url_name

* got rid of the hackish conversions between ' ' and '_'
* use url_name and display_name where appropriate
* update templates to match.

* cleaned up error module:
  - only one template
  - save error message in xml and reload
* better display of problem definition and metadata to staff
* save error messages as string, not exception objects.

Added more styles for the info page and added headers for the updates and handouts so they will be consistant for every class

* Log formatted traceback string instead of exc_info tuple itself
* display as a list

* call error tracker when needed
* remove duplicate logging--just add info and re-raise
* xml modulestore uses error tracker to capture load errors
* add unstyled list of import errors to courseware homepage!

Got profile page working again. The grader for each course is now defined in the data dir as grading_policy.json.

Add optional hide_from_toc attribute to XML elements to support Tutorials (which don't show up in the navigation).