better data entry needed for gradebook, to speed instructor work

There are several issues related to speeding data entry. The first is a current bluprint, which asks for a "filldown" command, that will fill a column with the same grade.

We also need to clean-up how the arrow key is handled different by the app / browser, than the tab key. The tab key highlights an existing grade in a cell. The arrow key blows the grade away. But if the cell is left blank and the blank is committed, there is no change made to the cell. The arrow key and tab key should work the same, and we may want for the blank to be interpreted as a "-". Otherwise, instructors will think they are deleting scores when they are not. A big problem.