Fix defunct process issues: create Proc class (#4210)

* Proc class
Encapsulate processes in a class, when they go out of scope, we can use the __destruct() process to make sure the process terminates.

* Fix rrdtool_last checks failing

* Don't close rrdtool in rrd_graph
Try to start rrdtool process if they haven't been started yet
Remove some extra debug output

* phpdocs added
several cleanups
should still be functioning the same
Only open one  rrdtool process for graph.php

poll-billing.php

@@ -158,4 +158,4 @@ if ($poller_time > 300) {
 }
 echo "\nCompleted in $poller_time sec\n";
 
-rrdtool_terminate();
+rrdtool_close();