Use CodeBuilderContext instead of CodeGeneratorContext.
Use Microsoft.AspNet.Razor.Runtime project.
Configure host to utilize tag helper types.

- Set the appropriate GeneratedTagHelperContext properties to ensure code is generated correctly.
- Set the TagHelperDescriptorResolver.

#1165
Add writing scopes to RazorPage.

- RazorPage now has the ability to use writing scopes to control where things are written.
- This enables RazorPages to use these writing scopes with TagHelpers.  TagHelpers use them to buffer attributes that have C# contained within them and to also buffer content of TagHelpers whos ContentBehavior is Modify.
- Added RazorPage tests to validate their functionality.

#1102
Add CreateTagHelper to RazorPage.

- The CreateTagHelper method is responsible for creating and activating TagHelpers.
- Added the support for requesting the ViewContext.
- Added tests to validate the tag helper creation mechanism.

#1104
Updated to work with latest Razor changes.
Cleanup tabs in project.json files
Use nameof when initializing `GeneratedTagHelperContext`

nits:
- missing blank line before a comment
- cleanup line breaks in `RazorPage.CreateTagHelper`
Tag Helpers: add `ModelExpression` class to support `Expression<Func<TModel, TValue>>` attributes
- includes new `RazorPage<TModel>.CreateModelExpression<TValue>()` method
- #1240

nit:
- regenerating the resources reordered Microsoft.AspNet.Mvc.Core's Resources.designer.cs
Add copyright notices to new files
Add missing access modifier
Add ITagHelperActivator.

- The TagHelperActivator enables dependency injection via properties and allows access to the ViewContext.
- This replaces the ICanHasViewContext mechanism that we had in place before.
- Added tests and fixed up existing to work with new format for providing ViewContext.

#1258
Removed the TypeActivator from TagHelper creation.

- We now new up TagHelper's, requiring them to have parameterless constructors.
- Added test to validate throwing.
- Removed existing tests that expected the constructor injection behavior.

#1303
Add TagHelper functional test.

- Added an end-to-end test that verifies all content behaviors, interactions and functionalities of tag helpers.
- Added some common user scenarios to verify that the system works how we expect.

#1116