- aspnet/Testing#248
- xUnit no longer supports .NET 4.5.1
- update AppVeyor config so this framework version is available
- build tests for desktop .NET only on Windows
- `true` has the opposite meaning now but most changes are due to new parameters names in `IViewEngine`
- use name names in `Microsoft.AspNet.Mvc.ViewFound` and not found events
- remove `IRazorPage.IsPartial` and `RazorView.IsPartial`
- remove `IsPartial` properties from `Microsoft.AspNet.Mvc.Razor.BeginInstrumentationContext` and end events
- add parameter checks to `RazorView` constructor; instances are not retrieved from DI
nits:
- remove unused `cacheKey` parameter from `RazorViewEngine.CreateCacheResult()`
- correct duplicate test names in `RazorPageTest`
- also `...OnPageExecutionListenerContext` -> `...OnPageExecutionContext`
- use `MvcTestFixture` instead of `TestHelper`
- part of #3139
- continue to test e2e interaction of `FlushAsync()` with sections, partials, et cetera
- remove `FlushPointTest.FlushBeforeCallingLayout()`
- `RazorPageTest.FlushAsync_ThrowsIfTheLayoutHasBeenSet()` unit test covers the scenario