Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

META MODE: These need object directories to handle staging.

Sponsored by: EMC / Isilon Storage Division

Follow-up to r255036; remove beforeinstall directives from bsdconfig(8)
Makefile's, fixing concurrent installworld (`make -j17 installworld').

Thanks to: delphij, emaste
Reviewed by: delphij
MFC after: 3 days
X-MFC-to: stable/10, stable/9

Import media selection/preparation framework (sysinstall inspired). Makes
accessing files from various types of media nice and abstracted away from
the wet-work involved in preparing, validating, and initializing those
types of media. This will be used for the package management system module
and other modules that need access to files and want to allow the user to
decide where those files come from (either in a scripted fashion, prompted
fashion, or any combination thereof).

Heavily inspired by sysinstall and even uses the same reserved words so
that scripts are portable. Coded over months, tested continuously through-
out, and reviewed several times.

Some notes about the changes:
- Move network-setting acquisition/validation routines to media/tcpip.subr
- The options screen from sysinstall has been converted to a dialog menu
- The "UFS" media choice is renamed to "Directory" to reflect how sysinstall
treats the choice and a new [true] "UFS" media choice has been added that
acts on real UFS partitions (such as external disks with disklabels).
- Many more help files have been resurrected from sysinstall (I noticed that
some of the content seems a bit dated; I gave them a once-over but they
could really use an update).
- A total of 10 media choices are presented (via mediaGetType) including:
CD/DVD, FTP, FTP Passive, HTTP Proxy, Directory, NFS, DOS, UFS, Floppy, USB
- Novel struct/device management layer for managing the issue of passing
more information than can comfortably fit in an argument list.

Resurrect usage.hlp and securelevel.hlp from sysinstall(8) and integrate them
into bsdconfig(8).

Approved by: adrian (co-mentor) (implicit)

More-accurately replicate the help system from sysinstall(8). However, also
improve upon the system by giving the user a "Help" button instead of requiring
the user to press F1.

NOTE: In FreeBSD-9 and higher, dialog(1) does not support the F1 hook, so the
mechanism for providing help to the user had to be changed to a button.

This now means we can resurrect *.hlp files from usr.sbin/sysinstall/help/ as-
is and reusing them as-needed in bsdconfig (holding to the goal of losing as
little functionality from sysinstall as possible).

Reviewed by: adrian (co-mentor)
Approved by: adrian (co-mentor)

Move major includes into /usr/share/bsdconfig for easy external access.

Reviewed by: adrian (co-mentor)
Approved by: adrian (co-mentor)

Import bsdconfig(8) as a replacement for the post-install abilities of
deprecated sysinstall(8). NOTE: WITH_BSDCONFIG is currently required.

Submitted by: Devin Teske (dteske), Ron McDowell <rcm@fuzzwad.org>
Reviewed by: Ron McDowell <rcm@fuzzwad.org>
Approved by: Ed Maste (emaste)