improved javadoc/goal documentation

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1561479 13f79535-47bb-0310-9956-ffa450edef68
fixed typo

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1561480 13f79535-47bb-0310-9956-ffa450edef68