Add download many results and predictions

[nicomy]

@ mention of reviewers

@ObadaS

A brief description of the purpose of the changes contained in this PR.

• Add the possibility to download results and prediction, with minimal DB queries.
• Download results will includes both detailed result file and score file.
• When downloading predictions or results, only finished submission are donwloaded

A checklist for hand testing

• Test downlad prediction and results
• Test with large amount of submissions
• Test download many and heavy detailed restults.

Checklist

• Code review by me
• Hand tested by me
• I'm proud of my work
• Code review by reviewer
• Hand tested by reviewer
• CircleCi tests are passing
• Ready to merge