@timholy could you please review this and the two linked PRs? thanks.

@bjarthur, @timholy - I could not find a documentation of contract for metadata function defined in FileIO.jl.

In parallel we are considering adding metadata function to DataAPI.jl.

I have the following questions:

• would it make sense for FileIO.metadata to add a method to DataAPI.metadata instead of creating a new function;
• in this case would it make sense/be possible to return e.g. NamedTuple instead of Tuple (in DataAPI.jl a natural interface is to return an object having key => value pairs)

Or maybe there is some other solution to the name clash?