This function determines whether to open a files-based Daf or an HDF5-based Daf based on the file path.
Details
If the path ends with .h5df or contains .h5dfs# (followed by a group path),
then it opens an HDF5 file (or a group in one). Otherwise, it opens a files-based Daf.
As a shorthand, you can specify a path to a group within an HDF5 file by using a path
with a .h5dfs suffix, followed by # and the path of the group in the file.
See the Julia documentation for details.