Enable filtering in plugins

Correct a severe bug in Processor::ProcessDataset. Before this commit
Processor evaluate all user-defined plugins even if some of them return
false. It does not affect event selection performed by PECReaderPlugin.

core/src/Processor.cpp

@@ -123,7 +123,7 @@ void Processor::ProcessDataset(Dataset const &dataset)
         for (unsigned i = 1; i < path.size(); ++i)
         {
             if (not path.at(i)->ProcessEvent())
-                continue;
+                break;
         }
     }