H5::File: explicitly pass the FileCreatPropList
Add test for creating and retrieving them in the same order
H5: File+Group ceep track of link creation order

We set up link creation order via H5Pset_link_creation_order,
so the groups can be access reliably via our `index` based
accessors.
See #issue 387 for details.
Merge tests for creation order from @jgrewe
Merge pull request #390 from gicmo/group_order

Keep track of link creation order in hdf5 - awesome!