Adding parameter replacement

Provides token replacement for attribute routing template using a syntax like:

`api/[controller]/{id?}`

With this change the use of controller and action as parameters in attribute routes is disallowed, and will reported as an error. This is the cool new way to do it, which will provide more consistent behavior, and better performance.

Majority of the changes here are to provide a good experience for reporting errors across all the attribute routes.
How do I represent a literal `[` and `]` in a route template? There is an escape syntax for `{` and `}` so we should look at that. That can make using a regex for the substitution rather difficult (which is why we don't use regexes for anything else in route parsing).