display template helpers can use a template name
changed how html conventions work with model templates

- There is now an [EditorTemplate] which tells html conventions to
render an EditorTemplates/[type_name].chstml .
- Removed html helper which uses model template, just use the asp.net
mvc helpers to render templates.
- Added TemplateModel() method which retrieves the template model when
rendering a model template. This can be used in view engine conventions.
- fixed a bug in Modelinfo.HasAttribute method. It will check for both
property of type and the type itself for the specified attribute.