- add `IHtmlGenerator.GetCurrentValues()` method
- bring together bits of `GenerateSelect()` and `UpdateSelectListItemsWithDefaultValue()`
- get rid of ugly `out` parameter
- also allows `<option/>` tag helpers to run before `<select/>` helper generation
- match `null` values and `SelectListItem`s with empty values
- match `enum` names correctly
- add doc comments for `IHtmlGenerator.GenerateSelect()` methods
Doug Bunting