Add WithTraceStyle extension member to Plotly.NET.CSharp

[kMutagene]

See #434 which demonstrated the need for this quite well

This also means we have to come up with a way to port the various TraceStyle functions to C# - and here we just might not get past the issue with many generic type arguments, because these functions can have up to 100 arguments. But as they are intended for expert use, this should be fine.