Add `ModelMetadata.HtmlEncode` property
- use new `ModelMetadata.HtmlEncode` property in HTML helpers
 - specifically in default HTML display and editor object templates (e.g.
   `@Html.DisplayFor()`) when value is non-`null` and the template is invoked
   with template depth greater than 1
- similar to MVC 5.2 commit [2b12791aee4f](https://aspnetwebstack.codeplex.com/SourceControl/changeset/2b12791aee4ffc56c7928b623bb45ee425813021)

nits:
- remove dupe `null` check in `DefaultDisplayTemplates.ObjectTemplate()`
- move backing fields initialized with constants together in `ModelMetadata`
Fix #1502 - Remove duplicate unit tests
Regenerate .kproj files
- does not seem to have a negative impact
- e.g. sample web projects run / debug fine
Accept VS changes to avoid noise later
renaming TraceType to LogLevel
Updating to release NuGet.config
Merge branch 'release' into dev
Adding support for excluding types for validation, based on type names for body bound models.
Updating to release NuGet.config
Merge branch 'release' into dev
Fixing dev NuGet.config
React to aspnet/Razor#208 changes.
Extend `IHtmlGenerator.GenerateSelect()` to make selected values available

nit: use Linq methods, not query syntax in `DefaultHtmlGenerator`
Provide selected values to `<option/>` tag helpers
- value may remain in the `FormContext` beyond `</select>` end tag but will
  be cleaned up at the `</form>` end tag of the containing `<form/>` element
 - `SelectTagHelper` called prior to helpers for contained `<option/>`s and
   not again later
- adjust mock setups to handle new `GenerateSelect()` call
- add assertions for expected `FormContext.FormData` entry

nit: mention #1468 in a test comment
Add `<option/>` tag helper
- #1423
Changes to support viewstart compilation