support more actions and add syslog-ng integration

* Support stop, status, restart actions.
* Add syslog-ng integration.
  - disabled by default (INTEGRATE_SYSLOG_NG=false)

syslog-ng integration:
* Host(Must): Define destination d_docker
* Container(Must): Start syslog-ng process
* Container(Must): syslog-ng must reads /dev/log and
  writes to /log . like the following example (syslog-ng.conf):

	source s_src {
		unix-dgram("/dev/log");
		internal();
	};

	destination d_socket {
		unix-stream("/log" keep-alive(yes));
	};

	log {
		source(s_src);
		destination(d_socket);
	};

* Container(Recommend): Add the following line
  to /etc/default/syslog-ng :

	SYSLOGNG_OPTS="--no-caps"

  This config avoids warning message like the following
  when syslog-ng is starting (real message is 1 line):

	syslog-ng: Error setting capabilities,
	capability management disabled;
	error='Operation not permitted'
use LSB log_* functions instead of echo
remove/add sample config
use LSB log_* functions
always restart syslog-ng if config dir exists

Because config files may be deleted
even if $INTEGRATE_SYSLOG_NG = false .
syslog-ng: use 'reload' instead of 'restart'
add option SKIP_STOP_WHEN_SHUTDOWN
remove unnecessary log_* messages
check syslog-ng is running before 'reload' action