Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Add example script `add_some_packages.sh', demonstrating how to install
a list of packages using the bsdconfig(8) API, providing dialog(8) based
user experience (versus plain console output were you to use pkg(8)
directly to install the same list of packages).

Remove example script `browse_packages_ftp.sh', made obsolete because
the digests.txz and packagesite.txz databases for pkg(8) are not
available via FTP (HTTP only to pkg.freebsd.org SRV hosts).

Update example script `browse_packages_http.sh', made to work with new
pkg(8) demonstrating how to generate a local package repository.

Fix a bug in `bsdconfig packages' where packages were listed twice. This
fix requires pkg(8) version 1.2.7_4 or higher.

NB: It is the introduction of pkg(8) 1.2.7_4 wherein I am also able to
drastically reduce the generation time of package dependencies prior to
the dialog display (by utilizing the new `-I' flag to pkg-rquery(8)).

While here, fix a positional argument nit for f_index_initialize() of
`packages/index.subr' include (the one and only argument is positional
argument 1 to state the by-ref handle, indicating the variable to set
in the caller's namespace; the nit I'm fixing here is that we were
querying positional argument 2 for this information incorrectly; caused
by a missing hunk back around SVN r257795).

Fix a bug in sysrc(8) described by PR bin/187458 "sysrc(8) silently and
unexpectedly bootstraps pkg". This was caused by an explicit entry in
`/usr/share/bsdconfig/common.subr' (used by sysrc(8)) that called pkg(8)
to populate the $PKG_ABI global (called in a way that allows implicit
bootstrap of pkg(8)). The solution to which was to find every place in
bsdconfig(8) that requires the $PKG_ABI global and add a layer of
protection by way of introducing the new API call f_musthavepkg_init()
(provided by new include, `/usr/share/bsdconfig/packages/musthavepkg.subr'
intented to mirror `/usr/share/bsdconfig/mustberoot.subr'). When the
$PKG_ABI global is required, you can use `f_musthavepkg_init' to cause
graceful premature termination in the event that pkg(8) has not yet been
bootstrapped, and thus cannot be used to populate $PKG_ABI.

NB: If running interactively ($nonInteractive is NULL or unset), the
f_musthavepkg_init() API call will attempt to bootstrap pkg(8), but only
if the user chooses "Yes" to a Yes/No dialog confirming it is ok to
bootstrap.

While here, simplify an if-conditional in `media/http.subr' include to
use sh(1) inline assignment-with-break.

Also, fix a bug in `media/http.subr' and `media/httpproxy.subr' wherein
the error messages for various HTTP failures were not finding their way
to the console (needed to pass stdout to pass-thru descriptor).

While here, remove the executable bit from `packages/categories.subr',
`packages/index.subr', and `packages/packages.subr' includes.

Fix issues where pkg(8) complains about PACKAGESITE being defined.
Previously, we would set $PACKAGESITE and export it. Now we only set
$PACKAGESITE for invocations of "pkg update" -- getting rid of all the
spurious warnings about PACKAGESITE being deprecated (it's still used
in the case of "pkg update" for simplicity versus having to configure
a config-file).

Remove the leading argument from invocations of f_index_initialize() in
`packages/packages.subr' include. The leading argument no longer means
what it used to, pre SVN r257995).

PR: bin/187458
Reviewed by: nwhitehorn
MFC after: 1 week
X-MFC-to: stable/10, stable/9

Implement GEOM based media device classification. You'll notice a few
different things from this commit:
+ More devices. Devices that were previously ignored are now present.
+ Faster device scanning. "There is no try, only Do" -- f_device_try()
is no longer the basis of device scanning as GEOM provides [nearly]
all devices (doesn't provide network devices).
+ More information available as non-root. Usually you have to be root
to do things like taste filesystems, and that limits the amount of
information available to non-root users; with GEOM, we see all even
running unprivileged as the brunt of information (except for so-
called ``dangerously dedicated'' file systems) is represented by the
`kern.geom.confxml' sysctl(8) MIB.
NB: Only really useful for external scripts that use the API and run as
non-root; where this code is used in bsdconfig(8) and bsdinstall(8)
you are running as root so can detect even ``dangerously dedicated''
file systems that are not present in GEOM; e.g., no PART class for
a DOS filesystem written directly to disk without partition table).
+ No more use of legacy tools such as diskinfo(8) to get disk capacity
or fdisk(8) to see partitions.

MFC after: 1 week

Fix a bug in HTTP checking/fetching.
Fix a bug in HTTP checking/fetching. Add Main Site to HTTP menu. Add new
example script browse_packages_http.sh and move existing example script
browse_packages.sh -> browse_packages_ftp.sh

Reviewed by: gjb, brd
Approved by: re (gjb), clusteradm (brd)
MFC after: 3 days