Add support for FileIO

[Beforerr]

It is registered in FileIO however neither load nor fileio_load is defined. Not sure if the following simple code is the correct way to do it.

fileio_load(file) = Arrow.Table(file.filename)

[Moelf]

It kinda is but it may also blow up user's RAM if the file is compressed and big

[Beforerr]

Do we intend to support FileIO? If so I may add the interface and improve upon this