WIP: Adding snapshot with V0 to data-regression

I think i need to add another factset to the repo before attempting another snapshot with the latest version, so that we can have a snapshot that is built incrementally from one with the old metadata and generates a new snapshot with the new metadata
> i'm pretty sure the VirtualDictionaryWindow is overkill for the bits

You you probably don't need that - it's only useful it want to guarantee you have a window, which in this case you don't. Just use `Dictionary`.