Added all remaining SchedulerDriver Methods

Added the followings to project:
* DeclineOffer() + unit test
* ReviveOffers() + unit test
* ReconcileTasks() + unit test
* ReconcileTasks() + unit test
* RequestResources() + unit test

@nqn I will correct.  The API itself is stable, but the internal impl still taking shape. Code reviews like this will help. Let's continue to do this.