Hotfix/optimize acceptor

See merge request jd-blockchain/bft-smart!24

* release/0.6.4:
  fixed dead lock bugs of consensus thread that the consensus lock is held by a waiting thread;
  fixed the bugs of concurrent competition between the process of consensus and the process of Heartbeat;
  refactored ReplicaContext;

# Conflicts:
#	src/main/java/bftsmart/consensus/roles/Acceptor.java

fixed the bugs of concurrent competition between the process of consensus and the process of Heartbeat;

fixed the bug that block the processing of consensus propose in Acceptor until the current node is ready;

Hotfix/jira 601 7nodes lc fail

See merge request jd-blockchain/bft-smart!23

* commit '48527fc2':
  fix bug: state transfer cross leader change , stop append should occur after state transfer complete
  fix state transfer bug, two node cannot state transfer at the same time
  fix bug: get app state exist bug, cancel get state from one replica temp

fix bug: state transfer cross leader change , stop append should occur after state transfer complete

* commit '00a15fe8':
  fix bug :state transfer,  when peer start, leader confirm task run after state transfer end

* commit 'f858ec43':
  fix bug: leader change process, proc sync msg, verify proof fail due to mac is null!

* tt:
  refactored;
  optimized HeartBeatTimer;

* feature/jira-601:
  optimized HeartBeatTimer;