[Fixes #731] Add unit tests for ReflectedActionDescriptorProvider

1. Added tests that cover parameters in actions.
2. Added tests that cover building the reflected application model.
3. Added tests that cover attribute routed action constraints and default values.
4. Added tests that cover conventionally routed action constraints and default values.
5. Refactored and cleaned up ReflectedActionDescriptorProvider. All the refactors consist
   of extracting blocks of code to separate methods to better display the flow when building
   the action descriptors.
isn't this basically the same test as `GetDescriptors_AddsParameters_ToActionDescriptor`