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.
Should an EvaluatorManager ever receive this message? From the other code it looks as if receiving this message triggers the instantiation of an `EvaluatorManager`. Receiving a second message would be an error, right?