[maven-release-plugin] prepare release sling-16

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1477524 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1477526 13f79535-47bb-0310-9956-ffa450edef68