Resource should implement standard pathlib-like interface

[lieryan]

What needed to be changed to make Resource, File, and Folder implement a pathlib-like interface:

1. Resource should implement os.PathLike Implement os.PathLike on Resource #738
2. File.read() should be deprecated, renamed to File.read_text()
3. File.write() should be deprecated,
4. File.write_text() and File.write_bytes() should be implemented
5. File.is_folder() and Folder.is_folder() should be deprecated, renamed to .is_dir() (done in Implement os.PathLike on Resource #738)
6. Implement Resource.is_file()
7. Implement the / operator as an alias to get_child()
8. Implement Folder.iterdir()
9. Folder.get_children() should be rewritten to call return list(self.iterdir())
10. Resource should inherit PurePath (rather questionable, Resource is not necessarily a Path on the filesystem, it may represent a file in a zipfile module)

The purpose here is not to make Resource usable in contexts where Path is expected, but rather simply just to standardize the vocabularies of path operations.

There is no plan to make Resource implement the entire pathlib interface; most of it doesn't make sense for rope's purpose and would only make using Resource class unnecessarily confusing (e.g. is_block_device() would never make sense for rope). If you need a real pathlib object, then access the Resource.pathlib property or convert the pathlib.Path(resource) which would use __fspath__ interface.