Initial Suggestions Resolution: VS2010, Project factoring, NUnit, IValidatable expressiveness

Implements the suggested changes for issues #7, #8, and #9 . 

In summary, this involves updating the solution/project files to VS 2010 format, using NUnit rather than the VS-specific test system, factoring the common model and JSON conversion classes into a project separate from the client-side portion of the library, and making the IValidatable.Validate method produce richer results.

I'm not completely satisfied with the name selections for the refactored projects, but they're probably good enough for now.