Scan an assembly in order to create a DataContractContentSerializer

Resolves #100.
To be clear, I only meant the following as a throw-away comment:

> Yes; and we could have, if we'd created two new implementations of ITypeResolver, instead of reusing TypeResolutionTable within the CreateTypeResolver methods.

We don't *need* to do that - in fact, now I'm sorry I wrote that at all, because it seems to derail us a little from the actual issue at hand.