Create end-of-semester form for seniors

[horcsinbalint]

Currently, seniors need to submit their report in PDF format by e-mail. It would probably be better if they could submit these PDFs via mars.

The challenges involved / please note:

• this depends on Problem with seniors and end-of-semester form #660
• it should be easy to download all reports at once by the people involved (e. g. downloading multiple files requires permissions from the browser, adding a dependency for zipping files might cause security risks)
• the deadline for these might be different from the forms provided for non-seniors
• the director might disagree with this request so it probably needs not to be implemented (this issue is only created to track this feature request that I received from the Student Council)
• seniors might not be required to fill out a form, they are only required to submit their report (i. e. the system might not have the authority to force them to answer if they want to continue with their senior status before they can submit their report)