Massive reorganization of code for the 4.0.1 branch.

- Reorganized types and namespaces to fit with current thinking.

- Removed features that are better implemented in other places (e.g., Mersenne Twister, random dice rolling).

- Added more extensions for various classes.

- Added an XInclude processing reader and a XML reader/writer decorator.

- Added a settings management system.

- Added lots of unit tests for various features.

- Established NuGet packaging for the library.