Add Turtle graphics

[Turtle graphics](https://en.wikipedia.org/wiki/Turtle_graphics) are a fun way to introduce people to program using visual output rather than textual output. I have run several successful outreach events using the [Python library](https://docs.python.org/3.7/library/turtle.html?highlight=turtle) and have also written a [C library](https://w3.cs.jmu.edu/lam2mo/cs240_2015_08/turtle.html) for it. A simple web search turns up several candidate implementations for Java, and having it easily accessible in Less-Java would facilitate doing similar activities. This would perhaps also help with #24.