Fix a few style errors while there.

(sshd) add HostKey to sshd_config to force available hostkeys. closes https://github.com/opnsense/core/issues/1200

Now that we have a plist it's easier to review/preview changes.
Can finally tackle the src/opnsense/contrib mess in a sensible
way with this and since we do not rely on mount/umount anymore.

When we build packages, we want to know if something is wrong.
For now, only use it in the upgrade path, not sure how to
to distinguish if a user or the build system is running the
package build.

Transition away from making the internals known, so rework
the whole tree.mk to expand better to dynamic destinations.

This is not hooked up yet, but we're more and more progressing
towards a package on top of FreeBSD.  The loader changes are
now handled via rc.loader.d, it makes sense to pll these two
files in as well, obsoleting the need to play tricks with src.git.

The file came from Scott Dale in 2007 like some of the others.
While there, also fix Deciso update from 2014->2016 in our tree.

See: https://github.com/pfsense/pfsense/commit/ab6a5cfc

(captive portal) handle transparant proxy from within ipfw, bit of a workaround for https://github.com/opnsense/core/issues/1189