Fix #14 - Add ability to choose Gradle version

When using tooling API - not available for deprecated launcher.
Minor cleanups.
Updated release notes.
[Gradle Release Plugin] - pre tag commit:  '1.12.5'.
[Gradle Release Plugin] - new version commit:  '1.12.6-SNAPSHOT'.
Merge branch 'gradle-1.12' into gradle-2.0.
Fixed merge conflicts.