Monitoring/Object: re-add process_perfdata

We would live better with unique column names on hosts and services

* Got introduced in 6095e440 and removed in c0e34473
* This might be a canditate for a regression test, as only graphers (PNP) are using this columns right now
* It makes IMO absolutely no sense to keep all those long column names in that object classes

modules/monitoring/library/Monitoring/Object/Host.php

@@ -130,7 +130,8 @@ class Host extends MonitoredObject
             'host_notes_url',
             'host_modified_host_attributes',
             'host_problem',
-            'host_process_performance_data'
+            'host_process_performance_data',
+            'process_perfdata' => 'host_process_performance_data'
         ))
             ->where('host_name', $this->host);
     }

modules/monitoring/library/Monitoring/Object/Service.php

@@ -191,6 +191,7 @@ class Service extends MonitoredObject
             'service_flap_detection_enabled_changed',
             'service_modified_service_attributes',
             'service_process_performance_data',
+            'process_perfdata' => 'service_process_performance_data',
             'service_percent_state_change',
             'service_host_name'
         ))