Move DifxApp.wixext into ext

src/.editorconfig renamed

src/ext/DifxApp/CSharp.Build.props renamed

src/ext/DifxApp/DifxApp.wixext.sln renamed

src/ext/DifxApp/Directory.Build.props renamed

src/ext/DifxApp/Directory.Build.targets renamed

src/ext/DifxApp/README.md renamed

src/ext/DifxApp/appveyor.cmd renamed

src/ext/DifxApp/appveyor.yml renamed

src/ext/DifxApp/nuget.config renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/DifxAppExtensionFixture.cs renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/TestData/UsingDriver/Package.en-us.wxl renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/TestData/UsingDriver/Package.wxs renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/TestData/UsingDriver/PackageComponents.wxs renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/TestData/UsingDriver/example.txt renamed

src/ext/DifxApp/test/WixToolsetTest.DifxApp/WixToolsetTest.DifxApp.csproj renamed

src/ext/DifxApp/wix.snk renamed

src/ext/DifxApp/wixext/DifxAppCompiler.cs renamed

src/ext/DifxApp/wixext/DifxAppDecompiler.cs renamed

src/ext/DifxApp/wixext/DifxAppExtensionData.cs renamed

src/ext/DifxApp/wixext/DifxAppExtensionFactory.cs renamed

src/ext/DifxApp/wixext/DifxAppTableDefinitions.cs renamed

src/ext/DifxApp/wixext/DifxAppWindowsInstallerBackendBinderExtension.cs renamed

src/ext/DifxApp/wixext/Symbols/DifxAppSymbolDefinitions.cs renamed

src/ext/DifxApp/wixext/Symbols/MsiDriverPackagesSymbol.cs renamed

src/ext/DifxApp/wixext/WixToolset.DifxApp.wixext.csproj renamed

src/ext/DifxApp/wixext/WixToolset.DifxApp.wixext.targets renamed

src/ext/DifxApp/wixlib/DifxAppExtension_Platform.wxi renamed

src/ext/DifxApp/wixlib/DifxAppExtension_x64.wxs renamed

src/ext/DifxApp/wixlib/DifxAppExtension_x86.wxs renamed

src/ext/DifxApp/wixlib/caSuffix.wxi renamed

src/ext/DifxApp/wixlib/difxapp.wixproj renamed

src/ext/DifxApp/wixlib/x64/DIFxApp.dll renamed

src/ext/DifxApp/wixlib/x64/DIFxAppA.dll renamed

src/ext/DifxApp/wixlib/x86/DIFxApp.dll renamed

src/ext/DifxApp/wixlib/x86/DIFxAppA.dll renamed

src/ext/global.json renamed

src/version.json renamed