fixed: Try to recache image in case cached texture loading fails

Up till now we didn't handle failed texture loading for cached images. This could occur in cases where the locally cached file is missing (or corrupt) and possibly other scenarios. 
Fair enough. If we somehow end up with a corrupted downloaded image it won't help. But if that happens it sounds like the vfs isn't doing its job? While I reckon off topic, I can't agree on the complicated part. It would be hidden a bit more as we move part to third party. I mean after all what our caching does is not very far from what a key value store does (stores a primary index and files to disk) so IMO would be nice to not having to maintain that code :)

Anyways. I missed what the discussion was about so consider my sidetrack academic :)