Promote DataPreconditionFailedException into the public Data Broker API

Extract DataPreconditionFailedException from Data Store Implementation
and make it part of public data store API as OptimisticLockFailedException
which still carries instance-identifier and message.

Introduce DataVerificationFailedException to Data store, to distinguish from
OptimisticLockFailedException.

Make sure OptimisticLockFailedException is propagated via all future
calls in MD-SAL to the client code.