Prefix portfolio and control submissions with team number

**Is your feature request related to a problem? Please describe.**
When I am judging for the Control award, I like to open all the submissions in tabs in my browser (Firefox). Because there are often many of them, the tabs get shrunk and the filenames truncated to the beginning. At this point, if I want to jump back to a particular team's submission, I need to remember which tab it was, or iterate. I'll occasionally open multiple portfolios, such as to prepare for panel judging or when deciding on awards, and the same difficulty occurs.

**Describe the solution you'd like**
When Portfolios and Control award submission PDFs are uploaded, save them with the team number prefixed if it isn't there already. Then when downloading, they will start with the team numbers, and it will be easier to see which document belongs to which team.

**Describe alternatives you've considered**
Two options:
1) Modify the filename upon download instead of upload. This would produce the same end effect, but it might make debugging more difficult if you can't find the filename in the backend because it no longer matches the filename produced when attempting to download it.
2) Change the requirements for teams submitting PDFs. This may be difficult as a surprise mid-season. Humans are unreliable at naming things per an exact syntax, and putting validation on the file upload for a correct name could cause a team to submit late if they were submitting at the deadline and didn't realize the new requirement existed.

**Additional context**

Thanks!

The issue names no files, tests, or entry points. Trace the upload handling for Portfolio and Control award PDFs, then verify that saved and downloaded filenames receive the team number prefix only when it is not already present.

Written by the indexing model from the issue text.