Feature request: show info about limits and retention in the upload form

[svh1985]

Hello!

I think it would be useful to expose some of the user set limits in the front-end. This way we can set expectations for the user and prevent errors.

1. Max individual file size limit
2. Max total bucket size limit
3. Show the file retention for one-time and un-downloaded files

These values should of course be populated with the values set in the config.js