Refactored the retrieval of the OnGet and OnSet methods to the `System.Type` extension method `GetGenericInstanceMethod()` that throws a meaningful, easilly debuggable, `MissingMethodException` if the methods can't be found.
Created `TypeExtensions.GetConstructor` extension method (with tests) and simplified WrappedPropertyProxyBuilder by using it.
Thinking about it, the previous release of Pomona should have been v0.11, because it was breaking. So bumping the version to 0.11 now.