fixup! Give the container some time to start up
Install GNOME and start a GNOME Terminal by default

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
fixup! Use Xpra's APT repository
Write the unix socket into /shared/

That way, we can access it easier and with better performance than
by ssh'ing into the container.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>