[Public Upload] Force password-protect public-uploads

[stephanarts]

Allowing unprotected public-uploads is a security risk. People could use your ownCloud instance to host illegal content from across the world. If ownCloud is running on the internet - instead of an intranet with VPN access, allowing anonymous upload without a password can be considered a security risk.

It would be nice if an administrative option could force users to set a password if they allow public uploads.

[stephanarts]

Should this be part of #4437?

[PVince81]

I'd say keep it separate, that other ticket already has too much in it. 😄

Also, this is a duplicate of #7341