[Backend] Don't serve images from UserContent

[nic547]

Currently images placed in /userContent will both be used for generating other sizes and formats and for serving to clients. I would prefer if that wasn't the case.

The requirements of the two usages are quite opposed to each other. As the "golden copy", the image should be high-quality, with little or no compression, so that I can use different formats or compression ratios at a latter date.
For serving the images to clients, I want maximum compression to reduce load times.

Therefore I don't want the image from userContent served to Clients.