Add rule parser and tokenizer

[ProfDoof]

I'm currently working on building out a new help engine that can handle a variety of cases including resolution of captures and lists, and to do so I need to be able to extract out pieces of the rules so I built out a rule tokenizer and parser.

I wanted to go ahead and get this out in draft format so people could discuss whether or not this was something we wanted to include since I already built it out and it only took a few hours.

[nriley]

From the community backlog session — improving help seems like an important goal. Your parser looks relatively lightweight and easy to read. We would want to see some kind of tests in community to make sure that with any changes to TalonScript it does not introduce any regressions.

Thank you for doing this!