Add setting to choose MsgPack mode

```C#
internal enum MsgPackMode
{
    Contract = 1, //StandardResolver
    Contractless = 2, //ContractlessStandardResolver
    Typeless = 3 // TypelessContractlessStandardResolver
}
```
I don't know how to do it right now, becaus I have to call `CompositeResolver.RegisterAndSetAsDefault` in a static constructor