- uses multicourse settings (default_chapter and default_section)
  - it would be nice to use course_settings instead, but that is not
    currently compatible with multicourse

Begin using a Keystore for XML parsing. Still broken: sequence icons, custom tags, problems, video js

uses new 'github_url' dict key in multicourse_settings
this replaces the previous "quickedit" functionality

* Wasn't passing coursename through to get_course_settings

filestore not None.  mitxhome.html now properly automatically lists
all courses given in settings.COURSE_SETTINGS.  mitxhome now served
from multicourse.views.  optioninput.html was missing; fixed. cleaned
up access to request.session for coursename in courseware/views.py