Implement StandardDispatch for AccessibleObject

[JeremyKuhne]

In order to make AccessibleObject trim friendly we'll need to implement StandardDispatch and replicate IReflect like we do in ExtenderProxy via ClassPropertyDispatchAdapter.

We don't handle fields / methods in ClassPropertyDispatchAdapter at this point (which AccessibleObject needs). Mapping for fields is in the class but is commented out.

It is important that we cache this in some way for given AccessibleObject types so that we don't incur the cost for every single control.

[JeremyKuhne]

Yay @lonitra!