Many Small problem enhancement

[molloykp]

Support command line argument for prefix of exercise (e.g., ex1, ex2, ). The program should then read each column that starts with the argument "ex1", like: ex1p1, ex1p2, ex1p3, ex1p4, ex1p5.

Map each of these to a rubric item on the indicated assignment, where each rubric item is named p1, p2, ..., pn.