- set correct `MarkAsHtmlEncodedMethodName` value in `MvcRazorHost`
- handle `HtmlString` values in `TagHelperOutput.Attributes` in `RazorPage`
- special-case double-quotes in `HtmlString` values
- add `static WriteTo()` method for use in tag helpers
- handle non-`string` `output.Attributes` values in tag helpers
- make `TagHelperContentWrapperTextWriter` a `public` class
- provide a `TagHelperContent.Append(object, ...)` extension method
- add `LinkTagHelper.Href` and `ScriptTagHelper.Src` properties
- avoid Razor HTML-encoding these attribute values before their use
- add `JavaScriptEncoder` properties in `LinkTagHelper` and `ScriptTagHelper`
- allow encoding testing without unit testing the default encoder
- handle MVC and Razor changes for this bug in existing tests
- add functional tests of encodings
- add test encoders to TestCommon project
nits:
- correct `InputTagHelper` to pass `type=""` through unchanged
- set correct `TagHelperContentTypeName` value in `MvcRazorHost`
- remove unnecessary `FormTagHelper.Method` and `OptionTagHelper.Selected` properties
- remove complex ternaries and `ShouldAddFileVersion()` methods
- add a few debug assertions
- fix some odd wrapping
- remove or `#if`-out unused `using`s
- remove trailing whitespace
