rc.d: add a service jails config to all base system services

This gives more permissions to services (e.g. network access to
services which require this) when they are started as an automatic
service jail.

The sshd patch is important for the sshd-related functionality as
described in the man-page in the service jails part.

The location of the added env vars is supposed to allow overriding them
in rc.conf, and to hard-disable the use of svcj for some parts where it
doesn't make sense or will not work.

Only a subset of all of the services are fully tested (I'm running this
since more than a year with various services started as service jails).
The untested parts should be most of the time ok, in some edge-cases
more permissions are needed inside the service jail.
Differential Revision: https://reviews.freebsd.org/D40371

Remove $FreeBSD$: one-line sh pattern

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

Limit access to system accounting files.

In 2013 the security chapter of the Handbook was updated in r42501 to
suggest limiting access to the system accounting file [*1] by creating the
initial file with a mode of 0600. This was in part based on a discussion in
the forums [*2]. Unfortunately, this advice is overridden by the fact that a
new file is created as part of periodic daily processing, and the file mode
is set by the rc.d/accounting script.

These changes update the accounting script to create the directory with mode
0750 if it doesn't already exist, and to create the daily file with mode
0640. This limits write access to root only, read access to root and members
of wheel, and eliminates world access completely. For admins who want to
prevent even members of wheel from accessing the files, the mode of the
/var/account directory can be manually changed to 0700, because the script
never creates or changes that directory if it already exists.

The accounting_rotate_log() function now also handles the error cases of no
existing log file to rotate, and attempting to rotate the file multiple
times (.0 file already exists).

Another small change here eliminates the complexity of the mktemp/chmod/mv
sequence for creating a new acct file by using install(1) with the flags
needed to directly create the file with the desired ownership and
modes. That allows coalescing two separate if checkyesno accounting_enable
blocks into one.

These changes were inspired by my investigation of PR 202203.

[1] https://www.freebsd.org/doc/handbook/security-accounting.html
[2] http://forums.freebsd.org/showthread.php?t=41059

PR: 202203
Differential Revision: https://reviews.freebsd.org/D20876

Move the rc framework out of sbin/init into libexec/rc.

The reasons for this are forward looking to pkgbase:
* /sbin/init is a special binary; try not to replace it with
every package update because an rc script was touched.
(a follow-up commit will make init its own package)
* having rc in its own place will allow more easy replacement
of the rc framework with alternatives, such as openrc.

Discussed with: brd (during BSDCam), kmoore
Requested by: cem, bz
PR: 231522
Approved by: re (gjb)