Got ApplicationTests working with new unit test project.

Had to fix the ApplicationTree and Application classes to lazily call the Cache method
(which is no renamed to EnsureCache) so that we could set the config location in the unit tests.
This should also improve performance a teeny bit and allow for better error handling if required.

src/SQLCE4Umbraco/Properties/AssemblyInfo.cs

@@ -18,3 +18,5 @@ using System.Runtime.InteropServices;
 
 // The following GUID is for the ID of the typelib if this project is exposed to COM
 [assembly: Guid("04436b0a-1dc6-4ee1-9d96-4c04f1a9f429")]
+
+[assembly: InternalsVisibleTo("Umbraco.Tests")]