added Toolchains menu with Standard/JDK/Custom entries

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1638226 13f79535-47bb-0310-9956-ffa450edef68
workaround for JDK requirement plugin info

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1638227 13f79535-47bb-0310-9956-ffa450edef68