Enhancement: save and load methods for AbstractPaths

[nickrobinson251]

Extend FileIO to define the save and load methods for AbstractPaths.

The default behaviour could be to serialize the data to an IOBuffer and call write(path, bytes).

[rofinn]

This has been brought up before. #22 (comment)

Unfortunately, we'd need to overload a lot of methods in FileIO for that to work nicely. Supporting the Stream interface would be easy enough if open(::AbstractPath) return some FileBufferr format that we controlled, but I think you're want to support the File API which will be more work. Also, almost none of the formats we currently use (at Invenia) support that interface. I think a better starting point might be to start refactoring FileIO.

FWIW, what does extending save and load get us apart from the file format detection?

[nickrobinson251]

The main benefit of extending save and load to AbstractPaths would be for non-local paths e.g. an S3Path, and so we don't have to keep track of when a "filepath" is a String or a *Path

[rofinn]

Right, but we'd need to modify the File type in FileIO for save and load to have the same behaviour. I suppose we could opt to only support a subset of the interface (e.g., use query to figure out the format and then only use the Stream type)?

[rofinn]

This is supported as of FileIO 1.3. Unfortunately, many backend file format packages assume filepaths are strings. We'll need to fix each package individually as they come up.