IPFW and PF are used for more than just firewall and shaper, e.g.
NAT, policy routing or shaping, and the plugin framework supports
registering multiple user-facing services per file.

pkg can display to-be-deleted packages, but won't resolve these
issues when triggered using "upgrade -n".  Thus, it's pointless
to try to keep this code until a newer pkg release can actually
cope with resolving the full upgrade cycle before upgrading.

This is the glue needed to be entirely plugin-agnostic, it only
needs new hooks for spots we haven't pluginified yet.  The dns
subsystem is another likely candidate in the long run.

Allows to move these plugins away from core: bsnmpd, igmpproxy,
relayd, miniupnpd.  ACL and menu entries pending...

.. with either IGMP or FTP proxy.

It's difficult to say we can remove Relayd from base just yet.
Unbound and Dnsmasq sure are not going anywhere due to their
dependencies into DHCP.  Relayd is similarly intermingled.

fix bug in firewall_rules_edit.php reported by tillsense in the forum…

fix bug in firewall_rules_edit.php reported by tillsense in the forum at https://forum.opnsense.org/index.php?topic=3951.0;topicseen