Persist conntrack database across reboots
Turns out, it does not work right now with packaged versions of the conntrack-tools, but it works with the not yet released changes. This commit introduces a save output format which will write the conntrack command line parameters needed to restore the conntrack tables. With this information it's easy to persist the tables. Unfortunately, it is unreleased. Building the conntrack-tools is easy, but it requires an up-to-date version of libnetfilter-conntrack which then might clash with system utilities that depend on a different version.