OpenIRT Todo List:

- Write real documentation beyond help file.
- Fix progress bars.
- Figure out what's wrong with help format.
- Add save chains option.
- Improve syntax.
- Add prior options.
- Add [if] [in] support.

Longer term issues:
- Add GPC model.
- Add EAP credible intervals (avoid because of memory issues for now).
- Add hierarchical priors.
- Add multiple groups.
- Check multimodality issues for MLE.
- Add manifest predictors (save varlist for these).
- Compare with BilogMG.