fully utilize Score-field in Submissions

Specifically, Submissions should feature a Score field (defaulting to 0) even if no Correction is available yet. This score of 0 can be distinguished from actually-reaching-0-points through the submission-state field. It would however make some calculations easier.

Things that need/should/could be calculated:

• Total reached Score so far
• Total reachable Score (min-max, to make it easier to tell if someone already failed/passed)

Places where this calculation (or the raw score field) needs to be implemented (correctly):

• students/[ID] in the Overview-Card
• in the SubmissionDatatable Component (regardless of where it is used)
• students/overview in the ParticipantDatatable Component