Allow proxying 3rd party assembly types

[BrunoJuchli]

Allow proxying 3rd party assembly types.

• specify mechanism to define which types to proxy and how to retrieve these
• maybe more along the lines of Castle DynamicProxy: Request the proxied type and
• Interface proxy: auto-create implementation
• Class-proxy: auto-create wrapping class, same public members etc, but implementation is forwarded to actual "real" instance of "real" class.

What are the downsides over the current approach? Currently a class-proxy means modifying the class to inserting method-decorating code and ctor-arguments, which is less than ideal as it makes it impossible to instantiate the class without proxying/interceptors.