Add CSV download button to Studio video upload page

@nasthagiri @clrux @BenjiLee 

http://studio.gwprice.m.sandbox.edx.org/videos/vpip/vpip/vpip
I considered using the list of all profiles in VAL, but I chose not to do so because I am concerned about profiles that are not applicable to a particular course for some reason. One scenario I am imagining is if there's some kind of test or dummy profile that gets added to prod, in which case we certainly don't want it showing up in all of these CSV downloads.