App Engine uses Java 7 and above

[elharo]

      <!--App Engine uses Java 6 and above-->
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>animal-sniffer-maven-plugin</artifactId>
        <configuration>
          <signature>
            <groupId>org.codehaus.mojo.signature</groupId>
            <artifactId>java16</artifactId>
            <version>1.0</version>
          </signature>
        </configuration>
      </plugin>
    </plugins>