The main use case here is storage provided versioning where we dont have
separate file ids for all the versions, by allowing a prefix for the
version we can store separate previews for all the versions.
Additionally, by keeping all the version previews in the same folder as the
"normal" previews they will be cleaned up properly when the file is deleted
Signed-off-by: Robin Appelman <robin@icewind.nl>
Robin Appelman