Fragment::create_from_file not supported with v2 files

[westonpace]

This method takes in a filename / path and synchronously creates the fragment metadata for it. We could potentially read the file footer to determine the version, this would be a change to the behavior of this function though as it would require a read where it previously did not.

We could also take the version in as arguments.

Either approach leads to a second issue. For v2 fragments we need a mapping from the dataset schema to the columns in the file. We record this when we create fragments but, if we are crating a fragment from a file, we would need some way to get that information. We could try and infer it by assuming the fragment schema equals the dataset schema (e.g. there are no columns to ignore, etc.).