Create ui specific meson.build

briar-gtk/briar_gtk/containers/add_contact.py

briar-gtk/briar_gtk/containers/login.py

briar-gtk/briar_gtk/containers/private_chat.py

briar-gtk/briar_gtk/containers/registration.py

briar-gtk/briar_gtk/define.py

briar-gtk/data/meson.build

briar-gtk/data/ui/app.briar.gtk.gresource.xml

briar-gtk/data/ui/meson.build

tools/generate_data.sh