Add CSV download button to Studio video upload page

@nasthagiri @clrux @BenjiLee 

http://studio.gwprice.m.sandbox.edx.org/videos/vpip/vpip/vpip
Is there a reason a new python library for CSV response was needed as opposed to using the existing ones used elsewhere in the platform (e.g., lms/djangoapps/instructor_analytics/csvs.py)?  If there's an issue with the existing ones, we should add a technical debt ticket for updating the others.  If not, we should add a technical debt ticket for consolidating these various implementations with a common platform-wide library for csvs.