- focus on affect of `ModelMetadata.HasNonDefaultEditFormat` and
`IHtmlHelper.Html5DateRenderingMode`
- work through `TemplateRenderer` because individual templates only do
formatting in a few cases
- XML comments for changed `TemplateInfo` properties
- correct `DefaultDisplayTemplateTests` and `DefaultEditorTemplateTests` namespaces
- add a couple of low-level `TemplateInfo` tests
- add more `DefaultTemplatesUtilities.GetHtmlHelper()` overloads, all
returning a strongly-typed helper
- also correct that method to ensure template helpers each get a unique
`IHtmlHelper` instance