a) Add a method to BatchRequestContent that is an overload of AddBatchRequestStep that accepts HttpRequestMessage as a parameter without having to provide an Id. Generate an Id using Guid.NewGuid.

b) Add another overload that accepts anything derived from baseRequest

The goal is to simplify creating batches for the simple case. Developers should be able to use GraphServiceClient to create request objects and just add them to a BatchRequestContent instance.

/cc @MIchaelMainer