API to get active and execution history of workflow instance

[mhnvelu]

Hi,

I think it would be good to have below APIs from the Runtime:

1. Current status - can return currently active states
2. Get execution history of workflow instance - can return completed/failed state in workflow instance
3. Get workflow data input and output
4. Get input and output data of a state

Thanks

[cdavernas]

@mhnvelu not only will be shipped with the overhaul I'm currently working on, but we are also working on a Dashboard SPA