* Remove the useless files

* Replace PermSize with MetaspaceSize, details see http://openjdk.java.net/jeps/122

* Update DLedgerCommitLog.java (#1145)

Delete useless code

* Remove the duplicate content

* Polish the comment (#1107)

* Minor Typo fix  (#860)

* [ISSUE #1082] Fix disconnection of HA (#1083)

* fixed the text description in chinese doc (#1339)

* fix /dev/shm not found on some OSs (#1345)

* Refactor the protection logic when pulling

* change the MQVersion variable to rocketmq 4.5.2 version;

* Minor polish

* Fix the wrong package name

* [maven-release-plugin] prepare release rocketmq-all-4.5.2

* [maven-release-plugin] prepare for next development iteration

* [RIP-15]Add Ipv6 support for RocketMQ

modify the format of concept.md