Add daemonization, fix any bugs found.

Add support for daemonizing via the --daemon flag. If daemonized, the
pid is written to the file provided via the --pidfile flag. When
daemonized, falco immediately returns an error if stderr output or
logging was chosen on the command line.

Clean up handling of outputs to match the expected use case (daemon):

 - syslog output is enabled by default
 - stdout output is disabled by default
 - If not configured at all, both outputs are enabled.

Also fix some bugs I found while running via packages:

 - There were still some references to the old rules filename
   falco_rules.conf.
 - The redhat package mistakenly defined some system directories like
   /etc, /etc/init.d. Add them to the exclusion list (See
   https://cmake.org/Bug/view.php?id=13609 for context).
 - Clean up some of the error messages to be more consistent.

After this I was able to build and install debian and rpm
packages. Starting the falco service ran falco as a daemon with syslog
output.

scripts/debian/falco

@@ -20,7 +20,7 @@ DESC="Falco"
 NAME=falco
 DAEMON=/usr/bin/$NAME
 PIDFILE=/var/run/$NAME.pid
-DAEMON_ARGS="--daemon --falcopid=$PIDFILE"
+DAEMON_ARGS="--daemon --pidfile=$PIDFILE"
 SCRIPTNAME=/etc/init.d/$NAME
 
 # Exit if the package is not installed

scripts/rpm/falco

@@ -34,7 +34,7 @@ start() {
     [ -x $exec ] || exit 5
     # [ -f $config ] || exit 6
     echo -n $"Starting $prog: "
-    daemon $exec --daemon --falcopid=$pidfile
+    daemon $exec --daemon --pidfile=$pidfile
     retval=$?
     echo
     [ $retval -eq 0 ] && touch $lockfile