Since this might break a few setups I'll postpone the zap
until after releasing the next snapshot on our road to 15.1.

The platform information should be used to identify a platform
type, not the product name.  Not sure why pfSense came up with
this, but now it's so deeply tied into the system that we can't
just take it out.  The platform type is also steered by the
installer or build tools at the moment.  We will change that,
but it'll take more testing.

Discussed with: Jos

Avoids the regeneration of the keys on reboot.  I guess this is what
people would expect.  ;)

* Sane defaults like FreeBSD: off, no root login, no passwords.

* Fix a bug in <sshdkeyonly/> handling.  Yes, it has been broken for
  ages.

* Boot into the installer by default; it can still be aborted.

* Remove the dysfunct rescue installer.  The normal installer
  now has a better rescue tool called "Import configuration".

* Move and rework the installer launcher as rc.installer.  It
  can be called at any time if needed.