Resolve "Assignment weights"

• Merged the two grading.html files we had since they were 95% identical.
• Made it such that there is a nice UI in the grading dialog to set assignment weights
• The simplest way to implement this was make a formula out of the weights and plug that formula in instead of having the logic in the backend.
• If the formula is set and the format is of ((assignment_1*3)+(assignment_2*2))/5 then the weights are filled in on the frontend.

Closes #25 (closed)