Move task and deploy modules in rally.objects

Change-Id: I144d02333b6f8cb42a6a13e38de5d58b755bc890
Implements: blueprint independent-deploy
Add tests for rally.objects.task.Task

Change-Id: I706a50b52d27a118dd6b7c98e2430a44a4c7dd6b
Implements: blueprint independent-deploy