Implement 'Priority' feature in reqnroll

[sampath-ganesan]

as we know MSTest supports Priority in the Unit test on each method, but when it comes to UI automation that is bit complex as we are using steps to execute our scenarios. if we could implement Priority feature for whole scenario that would help most of the UI testing. for example if we want to create user in first scenario and use that user to login in the next scenario this would help us in those type of cases.