fix the bug that tx_count_limit has decreased while the adjusted maxT…

…ransactions in a block can seal doesn't decrease (FISCO-BCOS#1042)

update ChangeLog.md (FISCO-BCOS#1000)

fix select null, because columnValue

fix compile demo failed

Merge pull request FISCO-BCOS#662 from FISCO-BCOS/release-1.3.8

Release 1.3.8

Merge pull request FISCO-BCOS#486 from FISCO-BCOS/release-1.3.7

Release 1.3.7

Update README.md

Update README.md