Frontend Caching system is caching all files from all proposals #200
Description
When using datalab the caching system is constantly caching files, it seems that it goes through all the proposals and is downloading all the small thumbnails to store, even if that proposal hasn't been opened.
This should be fixed by only caching images when they're requested by opening a proposal, this will add some loading time to when you open it but it should reduce the unnecessary downloading of images.