Implement the ability to provide objects as request body. The following use cases
are supported:
* raw objects: a JSON payload is created and the content type set to `application/json`
* text: the text is used as it is and no content type header is automatically added
* URLSearchParams: a form payload is created and the content type set to `application/x-www-form-urlencoded`
* FormData: the object is used as it is and no content type header is automatically added
* Blob: the object is used as it is and the content type set with the value of its `type` property if any
* ArrayBuffer: the object is used as it is and no content type header is automatically added
Closes https://github.com/angular/http/issues/69Closes#7310
Thierry Templier
Rob Wormald
Igor Minar