move the diff part to iFixPlusPlugin and refactor the code

Author: ChopinLi-cp

pom.xml

@@ -85,13 +85,16 @@
             <artifactId>idflakies</artifactId>
             <version>1.1.0</version>
         </dependency>
-
+        <dependency>
+            <groupId>org.xmlunit</groupId>
+            <artifactId>xmlunit-core</artifactId>
+            <version>2.8.2</version>
+        </dependency>
         <dependency>
             <groupId>org.apache.maven.shared</groupId>
             <artifactId>maven-invoker</artifactId>
             <version>3.0.1</version>
         </dependency>
-
         <dependency>
             <groupId>com.reedoei</groupId>
             <artifactId>eunomia</artifactId>