Adds ARIA labels to navigation

This includes calculator open/close button, navigation, profile, and
book's table of content.

First part of courseware refactor

Delete settings.py in favor of envs/*.py, and add a rake task to run a d...

fix multicourse; fix bug in I4xSystem - self.filestore not set when

Delete settings.py in favor of envs/*.py, and add a rake task to run a dev server locally from those settings

to show quickedit when settings.QUICKEDIT is True.  add
mathjax_include.html because that is needed by quickedit.html

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

More code transitioned to pyfilesystem

Added comments to Askbot stylesheets

Specific error handling

You can run this by do:

    bundle install (first time only)
    bundle exec guard

changes the border and box-shadow of headings in courseware content so b...

Conflicts:
	djangoapps/courseware/views.py