* [NOD-225] Finalize nodes below finality point
* [NOD-225] finalizeNodesBelowFinalityPoint only if dag.lastFinalityPoint is changed
* [NOD-225] change comment in validateParents
* [NOD-225] add string to ErrInvalidParentsRelation error
* [NOD-225] Change comment in validateParents
* [NOD-225] Change comment in validateParents
* [NOD-225] change comment in validateParents
* [NOD-225] Delete diff data from db directly from finalizeNodesBelowFinalityPoint
* [NOD-225] Refactor updateFinalityPoint