* fill in XDPoS_v2 variables and processQC/TC
* add timeout pool, refine engine variables
* refactor type functions
* solve a small pointer bug
* create general pool and its test, refine engine
* refine pool, add xdpos v2 config cert threshold
* refine config
* fix or skip tests due to PR-136 changes
* add bft receiver functions
* add bft receiver functions
* rename tc to TimeoutCert
* implement more functions
* New struct in consensus/XDPoS/utils/types.go, util functions, and test. (#14)
* define vote, timeout, sync info, qc, tc, extra fields in types.go, add test in types_test.go
* add json tag in types.go, refine encoder decoder of extra fields
* refactor types.go utils.go
* re-write types, comments
* add Hash SigHash for types, and tests
* define Round type
* remove unnecessary logs
* add temp functions
* add v2 engine functions placeholder
* typo fix on the consensus v2 function placeholders
* add countdown timer
* make initilised private to countdown
* push verify function
* add test on receiving vote
* revert type change
* add async on broadcast function
* add quit initial
* fix test
Co-authored-by: Jianrong <wjrjerome@gmail.com>
Co-authored-by: wgr523 <wgr523@gmail.com>
