RippleCalc: Stop using reference that might have been invalidated.
Initialize unassigned variable bConsumed.

* Assigned in the code, but only to false.
* Someday will get assigned to true.
Report whether a ledger is validated:
This addresses https://ripplelabs.atlassian.net/browse/RIPD-275
Use Json::StaticString to improve performance.
Use inject_error instead of manually adding errors.