Closes #13 and closes #14. Finished the TestCaseGenerator class which means the CsvModel (and any model, really) is now detached from the ShellTestCase classes (so they could be broken out into a separate tool/utility at some point). Added a static class ImageUtils.cs which has a method that can be used to copy Bitmaps. This method is used for bitmap copying due to issue #14 because I didn't want to wrap classes around Bitmaps and their backing stream objects as it would get a little ugly.

Moved all the Bitmap copying from RenderingController into the IImageComparer implementation (ExhaustiveTemplateComparer being the only concrete one right now) because the controller itself should be dumb and only pass data along, and because the fact that images should be 24 bit RGB are specific only to that image comparer.

Added a method to the IRenderlyAssetManager interface FetchToRandomFilename which was needed for test generation since at the time of test creation, there wasn't enough data to generate a proper test name without querying the model, and that is just crossing interface lines too much.