Add animated grade statistics report

The improvements to the gradebook in Moodle 1.9 resulted in an apparent loss of functionality in that the stats links are no longer available. Functionally this means that teachers and/or no longer have access median, mode, and standard deviation statistics. Since this is a loss of functionality, I am giving it a relatively high priority. When added to 1.9, it would be helpful if the teacher has an option of displaying the stats or not as sometimes it is preferred that class averages, max and min scores not be accessible to the student. For example, if there is a class where one student consistently has the highest score and students can see how that student did on an assignment the teacher may want to simply make stats not available to the students. This is discussed at:

http://moodle.org/mod/forum/discuss.php?d=84446

Below is a sample of what would be displayed on the stats page:

Highest: 100
Lowest: 0
Average: 88.88
Median: 93
Mode: 90
Standard Deviation: 18.76
Aggregate statistics include incomplete assignments, which show up as '-' these are counted as 0