Add support for Windows Phone

[AndrewJByrne]

The SettingsPane is not supported in Windows Phone. However, the APIs I use are supported. I just need a different UI metaphor to represent the DebugSettings dialog. This can be achieved with a Page.
The next decision is whether to add this to the solution, converting the solution to a Universal app, or just add the project, keeping them separate. The latter is trivial. The former is probably a better approach - but requires refactoring to share a reasonable amount of code between the projects.