Update to LetterGradeEarned and GradeEarned

DATASTD-1343 identified the need to record "non-standard" grade marks other than the typical A-F, such as "EE - Exceeding Expectations." This is particularly an issue for preschool and elementary grades, where reports of using "smiley faces" have been heard.

Letter grades are (in the data standard V4) strings of max length 20, originally structured to allow the flexibility to record grades such as A+ or B- or also to allow words such as "satisfactory," "meets standard," "improving," "needs improvement."

Letter grade strings are used in the following:.

• Grade.LetterGradeEarned
• LearningStandardGrade.GradeEarned
• PartialCourseTranscriptAwards.GradeEarned
• CourseTranscript.GradeEarned
• Grade.GradeEarned
• StudentGradebookEntry.GradeEarned

It is recommended that for both the attributes LetterGradeEarned and GradeEarned:

1. The max length be increased from 20 to 64
2. The documentation be updated to be more explicit as to the flexibilities allowed:
   "A final or interim (grading period) indicator of student performance in a class as submitted by the instructor. The grade may be expressed at a single letter (e.g., A-F); as a decorated letter grade (such as C+ or B-); as a descriptive term (such as "Satisfactory" or "Needs Improvement"; or a longer description (such as "EE - Exceeding Expectations").

The alternative to #2 is to update other online documentation.