Updates to c.m.r.d.context
  * Documentation updates
  * Moved inner named parameter classes to the new package `c.m.r.evaluator.context.parameters`

Also, renamed `onNext` in `JobMessageObserver` to `sendMessageToClient`
Merge pull request #780 from Microsoft-CISL/weimer_driver_API

Updates to c.m.r.d.context
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into shravan_groupcomm_interfaces