[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1632509 13f79535-47bb-0310-9956-ffa450edef68
update dependencies in release process to next snapshot version

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1632510 13f79535-47bb-0310-9956-ffa450edef68
update README

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1632511 13f79535-47bb-0310-9956-ffa450edef68