New CVS module for Scope work in progress

The new "scope-inprogress" CVS module is available for work in progress that may be incomplete and not ready for integration into the stable codebase.

To start with, I have checked in an STree implementation from dkodeih, an example of using SComboBox as an STable cell editor from Philippe Caron, and a bound ModelButton from mosesjones.

Feel free to use this module as a playground for new ideas!