Resolve "Add mqtt username and password to MQTTReceiver.java"

Adding Username and Password to ExternalHost thus removing these attributes from InfluxRoot and MQTTRoot

Closes #40 (closed)

eraser-base/src/main/jastadd/ItemHistory.jrag

@@ -7,9 +7,14 @@ aspect ItemHistory {
 
   public static final InfluxRoot InfluxRoot.createDefault() {
     InfluxRoot result = new InfluxRoot();
-    result.setUser(DEFAULT_USER);
-    result.setPassword(DEFAULT_PASSWORD);
+
+    ExternalHost eh = new ExternalHost();
+    eh.setUserName(DEFAULT_USER);
+    eh.setPassword(DEFAULT_PASSWORD);
+    result.setHost(eh);
+
     result.setDbName(DEFAULT_DB_NAME);
+
     return result;
   }