Update SclParser.java

The library has a problem of importing a whole SCD file which consists of several IEDs and that is because The dataSets Map is not cleared between switching of creating the next ServerModel of next IED.

src/main/java/com/beanit/openiec61850/SclParser.java

@@ -200,6 +200,8 @@ public class SclParser {
 
     ServerModel serverModel = new ServerModel(logicalDevices, null);
     
+    dataSetMap.clear();
+
     for (LnSubDef dataSetDef : dataSetDefs) {
       DataSet dataSet = createDataSet(serverModel, dataSetDef.logicalNode, dataSetDef.defXmlNode);
       dataSetsMap.put(dataSet.getReferenceStr(), dataSet);
@@ -207,6 +209,8 @@ public class SclParser {
 
     serverModel.addDataSets(dataSetsMap.values());
     
+    dataSetDefs.clear();
+
     return serverModel;
   }