This has no user-facing changes. It makes the internal handling of rules
much easier (no crazy duplicate rules in case our rules are added to
several backends).
It also fixes several open ends and small bugs in the process.
Events now generally carry the unique ID of the backend that is given
during initialization; there are a few more functions and other
bugfixes.
A few netcontrol tests are still broken (mostly due to a pcap update in
msater).