Add SystemML.jar to root of bin artifacts

In terms of documentation and understandability, having SystemML.jar at the root of the -bin.tgz/-bin.zip artifacts is useful. It is common practice on our project to describe using "SystemML.jar" (such as in the 'distrib' artifacts), but in the -bin artifacts, there is no "SystemML.jar" at the root, and the SystemML jar is located in the lib directory with a name such as lib/systemml-1.0.0-SNAPSHOT.jar.

Therefore, add SystemML.jar to the root of the -bin artifacts (and also keep the existing versioned jar in the lib directory).