Commented Feature: Update : [code/unity] Migrate application design to use Unity for IoC [1691]

Implement Unity and Dependency injection to enable the development of Unit Tests as Tweetinvi currently only have Integration tests.
Comments: Associated with changeset 34334: - Updated NameSpace of OAuthToken to TweetinviWebLogic
- Implemented a WebDownloader that is able to download online content synchronously or asynchronously
- Implemented DownloadProfileImage to IUser and IUserController
- Implemented a DownloadProfileImageAsync
- Removed old API examples
- Tested new code