plcont: Add TODO about recursive removal of folders
link: Add link.uri use to example
link: Split Link(value) to Link(uri/obj/sp_link)
link: Move Link(image) logic into Image.link
link: Move Link(user) logic into User.link
link: Move Link(playlist) logic into Playlist.link
link: Move Link(search) logic into Search.link
link: Move Link(artist) logic into Artist.link and Artist.portrait_link()
link: Move Link(album) logic into Album.link and Album.cover_link()
link: Move Link(track) logic into Track.link and Track.link_with_offset()
link: Remove Link(obj) support

The only remaining use case for direct usage of the Link class is to create a
link from an URI string: Link('spotify:track:2Foc5Q5nqNiosCNqttzHof')

A link to any object can be created by using the `link` attribute on the
object.