[WHISKER-13] Error during site generation with HelpMojo and Java8
- The version for maven-plugin-plugin was only specified for reporting, but not for build. Specifying it for build made the site generation succeed on Java 8.

git-svn-id: https://svn.apache.org/repos/asf/creadur/whisker/trunk@1622985 13f79535-47bb-0310-9956-ffa450edef68