Added the hack-fixed GradebookDetails report.
CLOSED - task 13: Gradebook Details Report - Add Case Coordinator to
header 
https://github.com/maine207/aspen/issues/issues/issue/13
The report header has been updated. The report now makes use of
ReferenceDescriptionLookup() when looking up reference code staff IDs
for the report header.
Merge pull request #46 from maine207/mbw/report-Hack-Fix

Mbw/report hack fix