Support FreeBSD

Greetingz,

I added a whitelist for FreeBSD so we pass the health_check.

The other commits are related to supporting native FreeBSD packaging, I made it optional (keyed by ENV['OMNIBUS_PKG_NATIVE']) so it doesn't change the nominal workflow..

The only changes inline to all workflows (in render_tasks) are:
1.) Swap out the package creation command if we're on freebsd and environment variable OMNIBUS_PKG_NATIVE is set.
2.) Create and remove a temporary exclusion file containing files to be excluded from the package (if any)

Dependencies (only if platform == freebsd and OMNIBUS_PKG_NATIVE is set)::
1.) FreeBSD ports tree installed (/usr/ports/Tools/scripts/plist)
2.) awk (bsd awk or gawk should work, included in base system).
3.) pkg_create (included in base system)

Cheers,
Brandon