First draft of typesetting engine

I implemented the Knuth-Plass algorithm. If necessary, I can simplify the code (the current version may work for circle or triangle-shaped text, [see this example](http://www.bramstein.com/projects/typeset/) but we don't need such advanced use).

The PostScript part still needs to be done.
For purposes of this book, it's best to expand acronyms when you use them :)  Our readers are junior developers, and so some may not be comfortable enough with data structures to have memorized that DAG means directed acyclic graph!