Add tests for FormTagHelper

- Modified FormTagHelper to utilize the AntiForgeryToken when the Action is URL based (different behavior).
Add AnchorTagHelper.

- Added a TagHelper that targets the <a> tag and allows users to do the equivalent of Html.ActionLink or Html.RouteLink.

#1247
Addressed code review comments and modified to use latest bits.
Fixed resources.
Add AnchorTagHelper tests.

- Fixed a typo in resource string.
Addressed code review comments.
Add ValidationMessage TagHelper.

#1250
Add ValidationMessageTagHelper tests.
Addressed code review comments.
Add ValidationSummaryTagHelper.

#1251
Add tests for ValidationSummaryTagHelper.

- Also addressed code review comments.