Option to hide make submission public button from participants

[ihsaan-ullah]

@ mention of reviewers

@Didayolo

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

Now organizers can enable/disable option for participants to make their submissions public. Option is available in the competition editor and in the yaml file

Editor:

YAML (only V2):

In this PR I have reorganized the competition edit page.

Documentation updated: https://github.com/codalab/codabench/wiki/Yaml-Structure#optional

Issues this PR resolves

• 1368

Checklist

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

[Didayolo]

Rebased develop to include CircleCI fix