add a recovery flag to proto to indicates communications from orphan eva...

This is for Driver HA. Add recovery flag in proto for marking communications coming from orphan evaluators started by previous driver (that crashed). This allows re-establishing communications between those evaluators and the reincarnated driver. 

Evaluator side change is currently done on the .NET side only.
Why does this need to be mutable? You create the object still in only one place, the `EvaluatorManagerFactory`, right?