FileObjectAPI.delete -> FieldFileObject.delete
FileObjectAPI.delete -> FieldFileObject.delete

This method isn't used internally and was getting masked by
FieldFile.delete. Move it to FileObjectAPI to preserve both API's.

ryneeverett/filebrowser-safe,ryneeverett/filebrowser-safe,ryneeverett/filebrowser-safe,ryneeverett/filebrowser-safe