Add AttributeCodeGenerator tests for enums, dictionaries, primitives

[NTaylorMullen]

TagHelpers default attribute code generator handles concrete types and depending on the TagHelper's attributes designates "correct" code generators to each. In the prototype the tag helper resolver and individual attribute code generators was part of MVC but after some research we found that it can be part of Microsoft.AspNet.Razor via #99. We can also translate the prototype based code generators from Mvc to Razor.

[yishaigalatzer]

This item is to test, and validate all the "special" cases like enums, dictionaries, collections (array/list/etc.).