changed INFO message: extractors ids are not really languages

git-svn-id: https://svn.apache.org/repos/asf/maven/plugin-tools/trunk@1648262 13f79535-47bb-0310-9956-ffa450edef68
[MPLUGIN-285] changed 'java' extractor id to 'java-javadoc' to match 'java-annotations'

git-svn-id: https://svn.apache.org/repos/asf/maven/plugin-tools/trunk@1648268 13f79535-47bb-0310-9956-ffa450edef68
improved documentation

git-svn-id: https://svn.apache.org/repos/asf/maven/plugin-tools/trunk@1648270 13f79535-47bb-0310-9956-ffa450edef68