- copy over legacy MVC's `SelectExtensions`, `SelectListItem` and `SelectListGroup`
- plus expected `SelectList` and `MultiSelectList`
- fixup select HTML helpers to meet WebFx standards and work in new world
- usual stuff: `[NotNull]`, `var`, `String` -> `string`, long lines, ...
- remove `IDictionary<string, object> htmlAttributes` overloads
- move longest extension method overloads into correct classes / interfaces
- add `ViewDataEvaluator.Eval()` overload for an `object` container
- rename lower-level helpers to make purposes more obvious
- nit: move Raw() methods up from bottom of HtmlHelper.cs
- use `DropDownList[For]()` in MVC sample