Adding pluginManagement for maven-plugin-plugin

* This fixes the problem when generating javadoc automatically that version/author are empty.
* BUT: site:site does not work since a plugin-plugin:2.7 cannot be downloaded - I don't see any references to that version.



git-svn-id: https://svn.apache.org/repos/asf/creadur/whisker/trunk@1631890 13f79535-47bb-0310-9956-ffa450edef68