[#942] Store the transaction log into database

[#1014] Support etcd3 as configuration center

[#1060] Do data validation when undo.

[#1064] bugfix:size wrong between xid and branchId

[#1074] bugfix:typos and replace AIT's with lambdas

[#824] Add time limit when transaction retry on the server.

[#1082] Cache configuration instance.

[#1084] Refactor Charset using and blob utils

[#1080] upgrade fastjson and nacos-client