Also, mark 1.20 as stable.

This puts together the bits from previous commits and actually allows
for activating a mode=mesh connection.

The functionality of the ibft settings plugin is now handled by
nm-initrd-generator. There is no need for it anymore, drop it.

Note that ibft called iscsiadm, which requires CAP_SYS_ADMIN to work
([1]). We really want to drop this capability, so the current solution
of a settings plugin (as it is implemented) is wrong. The solution
instead is nm-initrd-generator.

Also, on Fedora the ibft was disabled and probably on most other
distributions as well. This was only used on RHEL.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1371201#c7

It's deprecated and off by default for a long time.

It is bad to automatically reload connection profiles. For example, ifcfg
files may consist of multiple files, there is no guarantee that we
pick up the connection when it's fully written.

Just don't do this anymore.

Users should use D-Bus API or `nmcli connection reload` or `nmcli
connection load $FILENAME` to reload profiles from disk.