Fix implementation of inner_ext with a FunctionFunctorInterface

This pull request fixes the implementation of inner_ext with a FunctionFunctorInterface. Following commit SHA: b5caabd401cd61b9a4538de5aa8a9223755544fa from @wsttiger, all of the inner_ext methods have been overloaded to accept a shared pointer to a FunctionFunctorInterface. This will help with issue #78.