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

While here, remove the RAM disk mention, we can cope with this now.

cleanup in services_dnsmasq_configure, remove duplicate code, for https://github.com/opnsense/core/issues/1182

We only merge chunks for loader.conf leaveraging a priority scheme
in order to be able to override standard modifications made by e.g.
core or plugins (in case of user changes).

Start to work on its scripts, but 20-console is dynamic so it needs
more work in the actual PHP code.

Discussed with: @adschellevis

Reported by: Simon Brunet

PR: https://forum.opnsense.org/index.php?topic=3684

Expand / join the descriptive text and explain floating rules a bit more.