Add total_grade to grade_entry_students
Add total_grade to grade_entry_students
Updated calculating grade entry form marks and average

Moved calculate_total_mark(student_id) from grade_entry_form to
grade_entry_student and renamed to update_total_grade.

The total gets updated after every grade update.

The average gets calculated every time the student dashboard loads but
now just gets each student's total grade instead of looking at each
grade for each student.
Only save total_grade if it has changed
Changed calculate_total_percent to take a grade_entry_student and methods update total if nil
Update grade now supports deleting grades
Updated unit tests
Updated functional test
Merge branch 'issue-100'

Added total_grade to grade_entry_students.
Updating total_grade whenever a grade is updated.
Calculate_released_average now calls each grade_entry_student's total_grade instead of calculating it then.
Fix for issue-1001: added code to update group coverage when graders are randomly assigned to criteria
Fix for issue-1033 : all info is now updated when the result is marked as complete
Merge pull request #1288 from ariannedee/master

Fix for Issue-100: Refactor the code for calculating a student's average mark
Fix for issue-1211: added html_safe to unescape html <span> tag
Merge pull request #1291 from xiangyu89/issue-1001-fixed

Fix for issue-1001: added code to update group coverage when graders are randomly assigned to criteria
Merge pull request #1292 from xiangyu89/issue-1033-fixed

Fix for issue-1033 : all info is now updated when the result is marked as complete
Merge pull request #1293 from xiangyu89/issue-1211-fixed

Fix for issue-1211: added html_safe to unescape html <span> tag