Juwang-reef-webserver Unit tests

This request contains unit tests for reef-webserver. It is to resolve issue #819. In particular, it includes:
•	Test cases for HttpServer
•	Test cases for JettyHandler
•	Test cases for ReefEventStateManager
•	Test cases for HttpConfiguration
•	Tests for named parameters such as HttpEventHandlers, MaxPortNumber, MinPortNumber and MaxRetryAttempts are included in those tests
•	Tests for ParsedHttpRequest, TrackingUri and RuntimeSTartHandler have been covered in previous check-ins. 
This branch is from juwang-httpAvroSerilazer branch, which contains HttpAvroSerializer  and its complete test cases.