* debian/dcs.yml, debian/config.yml.in: New configuration templates.
* debian/patroni.install: Install new script to /usr/bin and configuration
templates to /etc/patroni.
Bump DH compat to 10 to get systemd integration; patch patroni.service to start
only if /etc/patroni/config.yml exists; install service file directly from
extras/startup-scripts/ instead of via debian/.