Requires the replacement of {COURSE_STATIC_URL} with just /static/
in about/overview.html files.

Added {COURSE_STATIC_URL} format key for about section html. Changed get_about_section to be get_course_about_section in courseware.courses.

The about image is now pulled from the course data directory and shown on the homepage, about course, and dashboard. Working on a way to show other, arbitrary course images.

Changed check_course from a decorator to a regular function that throws exceptions. Much easier to understand now.

This reverts commit 05e1bcf4.

The basic form has been fleshed out. Things still to do:
1) Extend get_course interface to the rest of modulestore
2) Make courses actually load
3) Make org/course/maybe others metadata attributes for course_module (see xml_module), so
that they are loaded/saved on import/export to xml

These are then displayed at /courses.

These are then displayed at /courses.