Performance improvements

Nothing special, just more documentation, more functional code and somewhat higher performance. The code is much easier on the eyes now, and more idiomatic Scala. There are no functionality changes in this release, except for the default halt state being the empty string instead of being a null or None.

This release is distributed as a JAR file, with the Scala runtime included into it. So you can run it by just using:
java -jar UTM.jar <parameters>, or you can use the included run.bat with the parameters.