handle db errors at higher level

@kushti This is the most important part to review. reportModifierIsValid and reportModifierIsInvalid now return Try so this is the "higher level" place where we propagated the DB errors to. I did not publish any event as this is neither semantically nor syntactically failed modification, it just cannot be persisted.

It differs as now DB errors leads to returning :

                UpdateInformation(history, updateInfo.state, Some(modToApply), None, updateInfo.suffix)

which would lead to another updateState call which is probably wrong, it is just to demonstrate that we are handling that effect now.

hyperledger-labs / Scorex

handle db errors at higher level #397