Submission pagination backend fixed

[IdirLISN]

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

Pagination display for submission in competition UI.
Using the existing file pagination.py inside of submissions viewset.

Dynamic pagination class added in pagination.py.
Get 50 objects by default.
Users can choose to get 50, 100, 500 or all objects.
"all objects" option is hard limited by max_page_size = 1000 per page.

Submission UI now displays 50 objects per page and a panel to enable the user to change this value.

Issues this PR resolves

• Closes No pagination in "Submissions" panel #2220

A checklist for hand testing

• Go to a competition with a lot of submissions and test the display of submissions inside of the competition page and inside of the organizer panel.

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

screenshot:

[Didayolo]

We need a third pagination size, something like 60 per page