[REQ][CSharp] Set EmitDefaultValue to true

Created by: B14m3m3

Is your feature request related to a problem? Please describe.

CSharp generated files have "EmitDefaultValue=false".

[DataContract]
    public partial class MyClass: IEquatable<MyClass>
    { 
        /// <summary>
        /// Gets or Sets MyVal
        /// </summary>
        [DataMember(Name="Unrealized",  EmitDefaultValue=false)]
        public double MyVal{ get; set; }`
        ...
    }

Describe the solution you'd like

There should be an option to not set this value (The default is true). It looks like there is a option on https://github.com/OpenAPITools/openapi-generator/blob/master/docs/generators/csharp-refactor.md. But i was unable to generate models with that generator.

So something like --additional-properties optionalEmitDefaultValues=true

Describe alternatives you've considered

None?