Cleanup and new extension method

Separated IContainerResult into its own file. Added a generic resolve
method as an extension method.
Added InjectionContainer.Clear() extension

Added the extension method Clear for the InjectionContainer for
debugging purposes.
Tests Cleanup

Removed commented code. Tests now invoke Resolve<T>() instead of
Resolve(Type). Test setup no longer creates a new container instance
every time. Test cleanup now empties the container's internal storage