Use the installer.sh from the source tarball

This redesigns how update works. installer.sh now rebuild the package,
stops the old code and starts the new code. Importantly, it does not
download the new package, this is left to the caller. cloudron-setup
downloads the code and calls installer.sh of the downloaded code.
Same goes for updater.sh. This means that installer.sh itself is now
easily updatable.

Part of #152

setup/container.sh

@@ -15,6 +15,8 @@ readonly CONFIG_DIR="/home/yellowtent/configs"
 readonly DATA_DIR="/home/yellowtent/data"
 readonly provider="${1:-generic}"
 
+usermod "${USER}" -a -G docker
+
 echo "=== Setting up firewall ==="
 iptables -t filter -N CLOUDRON || true
 iptables -t filter -F CLOUDRON # empty any existing rules