Created a DemoApp class, which will be used to create a Direct2D example app.
Modified WinMain function to run the demo app when the appropriate precompiler macro is defined.
TODO next: Use the demo app class to do something with Direct2D (part 3 of "Creating a Simple Direct2D Application" on MSDN)
Direct2D Demo App is now functional, use the program toggle in rMain.cpp to enable/disable it.