get known types for contaiers

Hello, i have some problems with container serialization in my project.

I've add a fix.

Also you can notice that i'm creating new instance of DataContractSerializerFactory beacurse if i take it from ServiceLocator it's already contains cashe from other not failed tests and results is different when running 1 and multiple tests.

Also i think it would be better to add chaching on level of GetKnownTypes / GetKnownTypesForInstance.

Sorry for thiss mess with revert.