Automatically delete old files

[matejdro]

I'm mostly using Zipline as a scratchboard for temporary file uploads. This means that I mostly upload files to it and then forget about them.

It would be nice if Zipline had an option to automatically delete old files (something like "delete files older than X days").

[matejdro]

I found this: https://zipline.diced.sh/docs/config/uploader#uploader_default_expiration

But even after setting it, it appears web interface still deafults to "Never".

[matejdro]

Converted to #624