Fix for running as a NuGet package

RProvider assembly isn't loaded when the DesignTime assembly is loaded
since it has no real dependencies on it. Also, the DesignTime assembly
needs to make sure that the AssemblyResolver that can find the RDotNet
assemblies is in place first, before anything else is done. This change
ensures that the AssemblyResolver is registered. Further, it places the
Configuration module strictly in the Runtime assembly which is
guaranteed to be loaded by both the RProvider and the DesignTime
assemblies. Always going through the same module ensures we can resolve
that module and retrieve the configuration for that module.