#100 Check in gradle-wrapper.jar

(Also updates the gradle scripts)

> To make the Wrapper files available to other developers and execution environments, you need to check them into version control. Wrapper files, including the JAR file, are small. Adding the JAR file to version control is expected. Some organizations do not allow projects to submit binary files to version control, and there is no workaround available. (https://docs.gradle.org/current/userguide/gradle_wrapper.html#sec:adding_wrapper)