leaderboard score precision added

@ mention of reviewers`

@Didayolo @bbearce`

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

In leaderboard scores are rounded to precision decimal points. precision can be provided in the yaml file as below

leaderboards:
  - index: 0 
    title: Results
    key: main
    submission_rule: "Force_Last"
    columns:
      - index: 0
        title: average auc
        key: auc
        sorting: desc
        precision: 3
      - index: 1
        title: average bac
        key: bac
        sorting: desc
        precision: 4

Issues this PR resolves

• Solved the long decimal number for scores in leaderboard
• Precision can be updated in the editor
• Documentation updated for precision
• V1 unpacker updated to take into account numeric_format
• V1 packer tested on V1 Iris bundle

Screenshot of solved problem

Leaderboard

Editor

V1 Unpacking numeric_format into precision YAML with numeric format

Converted numeric to precision as shown in the editor

A checklist for hand testing

• run docker-compose exec django ./manage.py migrate
• run docker-compose exec django ./manage.py collectstatic --noinput
• hard refresh (MAC: Command + Shift + R)

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