message: add support for link previews
New dependency on linkpreview library.
Note that also the use of ellipsize on the label+size_request doesn't really work well.
I don't think this here is really unit testable, and the linkpreview
library itself is tested.
If loading a lot at once seems to block GTK, idk why, all the fetching is in
another thread. Maybe loading the pixbuf files takes some
Closes #37 (closed)
This also includes the overall new foundation for message parsing, to start implementing it we just need to figure out embeding Gtk widgets in labels.
Edited by Raidro Manchester