Correct XML comment syntax
- fix problems at least with Roslyn compiler and VS IntelliSense or the Object Browser
 - `<see langref="keyword"/>` generates nothing
 - `<example>` at top level (outside `<summary>`) generates nothing
 - curly braces don't become angle brackets outside `<see cref="reference"/>` references
  - yeah, a point @yishaigalatzer asked about in a previous PR
- `<see href="reference"/>` is not valid
- correct some invalid use of angle brackets and remove useless empty elements
- correct unresolved XML comment references; generally, add namespace prefix

Symptoms for some of the above issues included
- generated XML comments such as `<!-- Badly formed XML comment ... -->`, usually indicating an unclosed element
- generated XML attributes such as `cref="!:..."`, indicating a broken reference
 - in a couple of cases we had `<typeparamref cref="TOption"/>`; attribute should be `"name"`

Few wording changes beyond
- `"opening </form> tag"` -> `"<form> start tag"`
- `"closing </form> tag"` -> `"</form> end tag"`

Also correct two typos in `HtmlHelper`

Will create a unit test to ensure XML syntax doesn't degrade going forward.  Separate PR.
- for now, check using `dir -r *.xml | sls '!'`
Updating release Nuget.config
Updating dev Nuget.config
Make HTML helper `null` handling consistent
- #874 lines 3, 4, and 6
- correct `Value()` to treat a `null` expression name the same as `string.Empty`
- add missing `[NotNull]` attributes in `EditorExtensions` and for `GenerateIdFromName()`
- consistently pass `null` for default expression names to the helpers
 - for example, from extension methods
- add test cases using `null` for expression name

nits:
- correct summary XML comment for `HtmlHelper` class
- use named parameters and prefer interface (not extension) methods in changed calls
- use `string.Empty` instead of `""` in a few tests
Call `IHtmlHelper` methods from extension methods
- don't call other extension methods
- #847 line 7
- remove extension methods that do nothing but pass through to the interface method
 - weren't exactly ambiguous (interface method wins) but were useless
Prefer `IHtmlHelper` methods elsewhere in our code
- #847 line 7 sub-bullets
- don't call extension methods from our templates
 - partially addressed in PR #934 (for methods changed there)
- don't reference extension methods from XML comments
Correct extension class names to match containing files
- #874 line 5
- `EditorExtensions` -> `HtmlHelperEditorExtensions`
- `SelectExtensions` -> `HtmlHelperSelectExtensions`
Remove incorrect references to `HtmlHelper` class
- extension methods extend `IHtmlHelper`
Routing related fixes for #55
Fix Challenge params order.
Correct gaps in PR #934
- correct XML comment typo introduced in `HtmlHelper` in 56d66c090eaedc33e4838437e7611ba2b9ca8929 (bad merge)
- fix missed `null` requirement for `@Html.RadioButtonFor()` and remove buried `null` check
- add back `Environment.Newline` to `@Html.TextArea()` (was dropped though comment wasn't)
Simplify some XML comment references
- follow VS fixup suggestion and change e.g. `<see cref="System.String"/>` -> `<see cref="string"/>`
Propogate additional compilation data from RoslynCompilationService
* Update CompilationFailedException to include path of file being compiled
* Pass in path being compiled to Rolsyn.
* Adding doc comments for compilation pieces

Fixes #869
Removing AdditionalInfo from CompilationResult since we can't always pass
it into exception thrown

All values in Exception.Data need to be serializable which is not true for
the diagnostics. Removing this property since we can't pass it through.
Fixing unit test
Data Token support changes
Reverting changes to sln file made in 01f5fec210ea864f8ed3637d775c4dc1a433524f
Making RoslynCompilationService a singleton.
 * Minor code cleanup from previous compilation related PR.
Test for XML documentation errors
- extend the "test" target in our build to use new k-xml-docs-test.shade command

Example output with one syntax error and one invalid reference:
```
info: Target xml-docs-test
warn: Invalid documentation syntax in src\Microsoft.AspNet.Mvc.Core\bin\debug\net45\Microsoft.AspNet.Mvc.Core.xml
warn:   3170: <!-- Badly formed XML comment ignored for member "T:Microsoft.AspNet.Mvc.Rendering.HtmlHelper" -->
warn:   3203: If the object is already an <see cref="!:IDictionaries&lt;string, object&gt;"/> instance, then it is
```
ProducesAttribute +
Adding Functional Tests

Conflicts:
	src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatter.cs
	src/Microsoft.AspNet.Mvc.Core/Resources.resx
	src/Microsoft.AspNet.Mvc.HeaderValueAbstractions/project.json
	test/Microsoft.AspNet.Mvc.FunctionalTests/project.json

Adding Resources + tests

Conflicts:
	src/Microsoft.AspNet.Mvc.Core/Properties/Resources.Designer.cs
	src/Microsoft.AspNet.Mvc.Core/Resources.resx

Adding produces content Attribute

Conflicts:
	src/Microsoft.AspNet.Mvc.Core/Microsoft.AspNet.Mvc.Core.kproj

Conflicts:
	src/Microsoft.AspNet.Mvc.Core/Microsoft.AspNet.Mvc.Core.kproj
	test/Microsoft.AspNet.Mvc.Core.Test/Microsoft.AspNet.Mvc.Core.Test.kproj