[maven-release-plugin] prepare release doxia-sitetools-1.6

git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia-sitetools/trunk@1606245 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia-sitetools/trunk@1606247 13f79535-47bb-0310-9956-ffa450edef68
autoVersionSubmodules=true

git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia-sitetools/trunk@1606251 13f79535-47bb-0310-9956-ffa450edef68