Set up flit for briar-wrapper

See merge request !2

Correct faq entry on contact transfer

See merge request !3

As mentioned correctly by @grote in
604c4e5f (comment 39593).

Closes
#2.

Unit test shouldn't fail in GitLab CI

See merge request !1

In Briar GTK, this stage is failing for a reason I don't understand:
briar-gtk#2

Here, it seems to work.

Because the two independent Briar projects briar_repl and Briar GTK
combine forces, the api wrapper part that used to be part of Briar GTK
now becomes a new project on its own: python-briar-wrapper.

With this commit, everything remaining from Briar GTK gets modified to
match python-briar-wrapper's needs.

Because the two independent Briar projects briar_repl and Briar GTK
combine forces, the api wrapper part that used to be part of Briar GTK
now becomes a new project on its own: python-briar-wrapper.

With this commit, everything specific to GTK and GNOME gets deleted.

If our alias matches the contact's nickname, it seems like Briar only
exposes the author's nickname and leaves out the alias field.

Also refactor socket_listener.py to make it more general.

With links back to base projects.

Also split up login and registration.

https://gitlab.gnome.org/World/podcasts/blob/bcd610e2e377d70ff75f52bbfae4d2007a248a90/CONTRIBUTING.md
https://gitlab.gnome.org/World/podcasts/blob/master/code-of-conduct.md

briar@9ebe49b8

It complains about duplicate import lines and I don't want to abstract
them now.

For this to work, you have to put this project (GTK) and Android's
project into one directory and call the Android's folder
"briar-android".