BulkParameters<T> cannot set _id explicitly

[maximpashuk]

https://github.com/Mpdreamz/NEST/blob/master/src/Nest/DSL/BulkIndexDescriptor.cs

Then I use BulkIndexDescriptor, I can provide Id value explicitly, so I don't need to have Id field in my document of type T.
In querying I can refer to builtin elasticsearch property _id.
Thats work fine.

https://github.com/Mpdreamz/NEST/blob/master/src/Nest/Domain/Parameters/BulkParameters.cs
Then I use BulkParameters I have no ability to set Id value explicitly.
I must have Id field declared in my document.
But will have some overhead: builtin elasticsearch _id property and explicit Id field with the same value.
Can query by any of them.

I don't want to have overhead by Id field.
As a workaround I can add JsonIgnore attribute to Id field, but I think this is more hack than workaround.

Since _id field in builtin in elasticsearch, I should have ability to set id in BulkParameters and do not have Id field in my index document.
Please add this ability.