Fixed category wise credit calculation

[megatron10]

The older version was under counting credits, since all S grade courses weren't being counted as valid credits. I have updated the code to correctly calculate total and category wise credits, whilst maintaining that the CGPA calculation is done independently (ignoring S graded courses). This is a necessary change as the S graded courses of the previous semester are supposed to count towards total credits. This has no undesirable side effect because of other S graded courses (like NSS/Clean India) as they are in the additional category and are not checked by default, thus aren't factored into the total credit calculation.

Before :-

After :-

Apart from this the indention has been made uniform.

[megatron10]

@AgamAgarwal @SaiHarshaK

[SaiHarshaK]

More context: Previous semester, we were given a choice to opt for letter grade or choose 'S' for the courses unlike other semesters due to the COVID crisis.
@megatron10 I think you should add "Audit" to the excludeList so that those credits are not added to the total credits count.

[frags51]

Also mention this clearly in documentation/in the list somewhere? That total credits includes 'S', but not additional. Will save confusion! @megatron10 @SaiHarshaK