* verify header including validator
* re-structure v1 v2 tests
* remove unused test function
* add test to check coinbase and validator address matches
* refactor engine v2 to group private functions into same file
* add isEpochSwitch function and refactor utils
* fix broken first v2 epoch switch block
* use adaptor epoch switch function to determine v1 v2 epoch swtich block
* add test for the GetMasternodesByNumber and GetCurrentEpochSwitchBlock function
* add v2 test for isAuthroisedAddress
* Use GetCurrentEpochSwitchBlock in findNearestSignedBlock api