Support format conversion on download

[rkhwaja]

OneDrive has a feature where they will convert the file format before downloading. Some of the pyfilesystem methods support an options dictionary which you could use to pass the format.

https://docs.microsoft.com/en-us/onedrive/developer/rest-api/api/driveitem_get_content_format?view=odsp-graph-online

[rkhwaja]

Can't do it as part of openbin because then it'll be written back in the same format