gradebook - fixed headers & columns progress commit

* basic functionality working
* moved to grader_report namespace
* resize is NOT working
* need to make code more readable
* need to add loading screen
MDL-46776 assignment: Add test data generator
MDL-25544 gradereport_grader: Improve Grader report user interface

* fixed resized event
* added 'overridden' text and fold graphic
* added loading screen
MDL-46658 gradereport: Update JS to meet coding style guidelines and fix various things
MDL-46731 gradereport_grader: Move tooltips to YUI module
Allow table attributes to be set on rows :|
MDL-46774 gradereport_grader: Move row/column highlight code to YUI module