Prepare for Engine release based on Sling API release

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1571625 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare release org.apache.sling.engine-2.3.0

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1571628 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1571630 13f79535-47bb-0310-9956-ffa450edef68
Update to Sling API snapshot during release vote period

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1571631 13f79535-47bb-0310-9956-ffa450edef68
Update to Sling API and Engine snapshots during release vote period

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1571632 13f79535-47bb-0310-9956-ffa450edef68