Implement CDBTransaction and CScopedDBTransaction
Implement CDBTransaction and CScopedDBTransaction

Allows easier commit/rollback handling, especially useful when AcceptBlock
fails and things need to be reverted.

thelazier/dash,biblepay/biblepay,nmarley/dash,ionomy/ion,UdjinM6/dash,biblepay/biblepay,dashpay/dash,nmarley/dash,dashpay/dash,biblepay/biblepay,UdjinM6/dash,ionomy/ion,dashpay/dash,nmarley/dash,nmarley/dash,UdjinM6/dash,UdjinM6/dash,thelazier/dash,UdjinM6/dash,biblepay/biblepay,biblepay/biblepay,biblepay/biblepay,biblepay/biblepay,thelazier/dash,ionomy/ion,ionomy/ion,nmarley/dash,nmarley/dash,biblepay/biblepay,thelazier/dash,ionomy/ion,dashpay/dash,nmarley/dash,dashpay/dash,ionomy/ion,thelazier/dash