* 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

Add Export Control Notice

* prepare to separate production-ready projects from the external projects

* Update fastjson to the latest stable version

* Clean code, don't list the default config in JVM

* Update README.md

* update the year info in NOTICE

* Release semaphore when timeout

* [ISSUE#525]add aclClient PRCHook for message track

* [ISSUE#525]add the apache license text,remove the merged from master branch

* [ISSUE#525]add aclClient PRCHook for message track,remove the merged content of notice and readme.md from master branch,add some unit test to increase the code coverage.

[ROCKETMQ-69] Add link to README.md for RocketMQ home, thanks @netroby, closes apache/incubator-rocketmq#47