Strip down sequence nav, start to use ems for font size instead of pixels and started to strip down the info page

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

Jarv/prod requirements

add back-compat code to customtag

* apparently 6002x is using the impl-as-child structure already.

Feature/victor/xml verify

Conflicts:
	lms/djangoapps/courseware/views.py
	lms/templates/profile.html

* 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!

* simplify logic--tracker just tracks errors.  Trackers should not raise,
      and are not be responsible for logging.
* adapted code to use trackers.
* Started cleanup of error handling code:
  - if need to add info and re-raise, just do that.  No logging.
  - if working around a problem, log and track as needed.

* get rid of dump to json
* formatting