[maven-release-plugin] prepare release org.apache.felix.utils-1.6.0

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1572002 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1572004 13f79535-47bb-0310-9956-ffa450edef68