wiki.freebsd.org/pkgbase maintenance

I'm aware that parts of <https://wiki.freebsd.org/pkgbase> are (or will 
be) outdated.

In particular: 
<https://wiki.freebsd.org/PkgBase?action=diff&rev1=129&rev2=130> was 
either contentious, or wrong. I didn't like removing '-r FreeBSD-base' 
from line 230, however doing so seemed better than the possibility of 
losing non-base packages. Compare with e.g. 
<https://github.com/FreeBSDFoundation/proj-laptop/issues/83>,


> … multi-stage upgrades of kernel, userland, and ports. It is necessary 
> to upgrade the kernel first and reboot into the new kernel before 
> upgrading the userland …