JDK 8: build fails due to JavaDoc checking issues

JDK 8 introduced stricter checking for JavaDoc processing, causing issues formerly producing warning messages to break the build.

Basically the fix is as easy as adding the following configuration to the pluginManagement section:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-javadoc-plugin</artifactId>
    <version>2.9.1</version>
    <configuration>
        <show>private</show>
        <additionalparam>-Xdoclint:none</additionalparam>
    </configuration>
</plugin>

To fix and close this issue, we need a testable build though which is currently blocked by WW-4402