[maven-release-plugin] prepare release org.apache.servicemix.bundles.gae-1.9.15_1

git-svn-id: https://svn.apache.org/repos/asf/servicemix/smx4/bundles/trunk@1639711 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/servicemix/smx4/bundles/trunk@1639713 13f79535-47bb-0310-9956-ffa450edef68