Before this commit, we had to do a separate query for every course a user was enrolled in when determining whether a course was refundable (if you have a certificate, it isn't). Now the student dashboard will make a one-time query to grab all of a user's cert-issued courses. This is indexed, so it should be much faster than grabbing each one separately.
common ------ This directory contains common code shared between LMS and CMS, such as Mako templates, CSS, and Coffescript.