Refactored the HTTP Client Implementation (#483)

* Initial implementation for batch send

* Unit tests for BatchRequestClient

* Finished sendAll() implementation

* Fixed some lint errors

* Fixed messaging test imports

* Adding more tests

* Increased test coverage

* Updated tests

* Implemented multipart parsing with dicer for performance

* Increased test coverage for HttpClient

* Added a test case for zlib

* Removed http-message-parser frm required dependencies

* Added some documentation

* Updated comments

* Trigger CI

* Implementing sendMulticast() API

* Added integration test

* Fixed some typos; Reduced batch size limit to 100

* More documentation and clean up

* Refactoring the http code

* Cleaning up the http client code

* Further refactored the AsyncHttpCall

* Added some comments

* Correct handling of entity check

* Refactored the HTTP request config processing out of AsyncHttpCall

* Cleaned up the HttpRequestConfigImpl class

* Making AsyncHttpCall constructor private

Author: hiranya911