[Fixes #734] Attribute Routing: Implement Name

1. Added support for Name in attribute routing. Name can be defined using [RouteAttribute]
and the different Http*Attributes, for example [HttpGet].

2. Names defined on actions always override names defined on the controller.

3. Actions with a non empty template don't inherit the name from the controller. The name
   is only inherited from the controller when the action template is null or empty.

4. Multiple attribute routes with different templates and the same name are not allowed.
use ```_namedEntries.TryGetValue(context.RouteName, out var entry)```
and remove ```AttributeRouteLinkGenerationEntry entry;```