Add support for [EnumMember] attributes

[robertcoltheart]

This allows us to have a level of compatibility with Java enums, while still maintaining proper .NET coding standards.

It makes sense to support this, since we already support [DataMember].

eg.

public enum MyEnum
{
    [EnumMember(Value = "MY_VALUE")]
    MyValue
}

[robertcoltheart]

Hi @AdrianStrugala, this is ready for review

[AdrianStrugala]

Hey Robert, Thank you for your PR. I will try to review it in next week. Adrian

[robertcoltheart]

Hi @AdrianStrugala, any chance you can push this out to Nuget?

[robertcoltheart]

Bump @AdrianStrugala