Add rail diagram generator

All languages currently use LaTeX and its rail package to generate railroad diagrams for the documentation. It would be useful if these diagrams can be generated directly from Eclipse.

The asciidoctor extension for generating such diagrams doesn't give good looking output and doesn't even work out of the box. Also, its input specification is different, causing the need to convert all existing diagram files. For these reasons, we opted for adding a rail diagram generator program.