GraphResponse object

[andrueastman]

This PR adds support for the GraphResponse object which will act as a wrapper for properties like the status code and http headers.

This work is done according to the spec found here.
https://github.com/microsoftgraph/msgraph-sdk-design/blob/master/GraphResponse.md

Currently, a user should be able to follow the following flow

BaseClient client = new BaseClient(requestUrl, authenticationProvider, customHttpProvider);
BaseRequest baseRequest = new BaseRequest(requestUrl, client);

GraphResponse<TestUser> returnedResponse = await baseRequest.SendAsyncWithGraphResponse<TestUser>("string", CancellationToken.None);
TestUser user = await response.GetResponseObjectAsync();

Fixes AB#4600