Gradle release v2.3.0 (#2486)
Gradle release v2.3.0 (#2486)

* [Gradle Release Plugin] - pre tag commit:  'v2.3.0-gradle'.

* [Gradle Release Plugin] - new version commit:  'v2.3.1-SNAPSHOT-gradle'.
GoogleContainerTools/jib,GoogleContainerTools/jib,GoogleContainerTools/jib,GoogleContainerTools/jib