Upgrade maven-site-plugin to 3.4 otherwise causes problems

during site generation with Maven 3.0.5 and above.

Author: khmarbaise

pom.xml

@@ -86,6 +86,11 @@
   <build>
     <pluginManagement>
       <plugins>
+         <plugin>
+           <groupId>org.apache.maven.plugins</groupId>
+           <artifactId>maven-site-plugin</artifactId>
+           <version>3.4</version>
+        </plugin>
          <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-gpg-plugin</artifactId>