IInputFormatter interface changes. 

1. Moving input formatting related classes to MVC Core.(for tests as well).
2. Cleaning up the IInputFormatter to the final version.
3. Updating the input formatters and the context to be compliant with the IInputFormatter interface.

- Not cleaning up TempInputFormatterProvider.
IMO it ain't broke and shouldn't be fixed. If we need to reduce boilerplate for tests we should focus on improving testability of things like ActionContext.