Prepare 0.15.6 release
Prepare 0.15.6 release

Compiled against the latest Gradle `Settings` API.

gradle/gradle,blindpirate/gradle,robinverduijn/gradle,gradle/gradle,gradle/gradle,gradle/gradle,blindpirate/gradle,gradle/gradle,gradle/gradle,blindpirate/gradle,blindpirate/gradle,gradle/gradle,robinverduijn/gradle,blindpirate/gradle,blindpirate/gradle,robinverduijn/gradle,blindpirate/gradle,gradle/gradle,robinverduijn/gradle,robinverduijn/gradle,gradle/gradle,robinverduijn/gradle,gradle/gradle,gradle/gradle-script-kotlin,robinverduijn/gradle,robinverduijn/gradle,gradle/gradle-script-kotlin,robinverduijn/gradle,blindpirate/gradle,blindpirate/gradle,robinverduijn/gradle,blindpirate/gradle,robinverduijn/gradle