[Gradebook] New Gradebook Keyboard Shortcuts for Assignment Statuses

[ehills]

In the New Gradebook, I can type EX to automatically get the Excused status applied to a student's grade for an assignment. I would love to see that functionality extended to the Missing and Late statuses as well. 

EX = Excused, M and L don't work.

Additionally, especially with external tools, it would be nice to have a T (Turned In) status to indicate what assignments have been submitted but not graded yet. This would be helpful for parents at the K-12 level.