- in lnurl.py, make request methods async
- in Qt GUI, lnurl network requests no longer block the GUI thread
- but they still do in the kivy GUI
- "lightning address" (LUD-16) support is removed for now as the
email addresses are indistinguishable from openalias email addresses
(both protocols should have added and enforced a prefix, or similar,
to remove this kind of ambiguity -- now we would need to make a
network request just to identify what kind of ID we were given)
Sometimes we want its "remember path" behaviour but it does not make sense to
parent the dialog from main window. When so, caller code no longer needs to
get a reference to a main window.
Also rm last usages of get_parent_main_window().
