feature: add PHP-FPM support for snmpd (#5912)

* add single pool based poller for php-fpm

* add the page for php-fpm

* add graph for php-fpm

* I agree to the conditions of the Contributor Agreement contained in doc/General/Contributing.md.

* use named OID as suggest by @laf

* document PHP-FPM monitoring

* link it in the index

* clean up the named oid

* add how to grab the script in question

html/includes/graphs/application/php-fpm.inc.php

@@ -0,0 +1,42 @@
+<?php
+require 'includes/graphs/common.inc.php';
+$name = 'php-fpm';
+$app_id = $app['app_id'];
+$scale_min     = 0;
+$colours       = 'mixed';
+$unit_text     = '';
+$unitlen       = 10;
+$bigdescrlen   = 15;
+$smalldescrlen = 15;
+$dostack       = 0;
+$printtotal    = 0;
+$addarea       = 1;
+$transparency  = 15;
+
+$rrd_filename = rrd_name($device['hostname'], array('app', $name, $app_id));
+
+$array = array(
+    'lq' => array('descr' => 'Listen Queue','colour' => '582A72',),
+    'mlq' => array('descr' => 'Max Listen Queue','colour' => '28774F',),
+    'ip' => array('descr' => 'Idle Procs','colour' => '88CC88',),
+    'ap' => array('descr' => 'Active Procs','colour' => 'D46A6A',),
+    'tp' => array('descr' => 'Total Procs','colour' => 'FFD1AA',),
+    'map' => array('descr' => 'Max Active Procs','colour' => '582A72',),
+    'mcr' => array('descr' => 'Max Children Reached','colour' => 'AA5439',),
+    'sr' => array('descr' => 'Slow Reqs.','colour' => '28536C',),
+);
+
+$i = 0;
+if (is_file($rrd_filename)) {
+    foreach ($array as $ds => $vars) {
+        $rrd_list[$i]['filename'] = $rrd_filename;
+        $rrd_list[$i]['descr']    = $vars['descr'];
+        $rrd_list[$i]['ds']       = $ds;
+        $rrd_list[$i]['colour']   = $vars['colour'];
+        $i++;
+    }
+} else {
+    echo "file missing: $rrd_filename";
+}
+
+require 'includes/graphs/generic_v3_multiline.inc.php';