update pom license, scm, maillists, issuemanagement, add DISCLAIMER

[diecui1202]

What is the purpose of the change

Update pom for into apache incubator, partial fix for this issue: https://issues.apache.org/jira/projects/DUBBO/issues/DUBBO-7?filter=allopenissues

Brief changelog

1. update pom.xml license
2. update scm, mailLists, issueManagement, organization
3. add DISCLAIMER

Verifying this change

All unit tests are pass

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a GITHUB_issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a GITHUB issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [Dubbo-XXX] Fix UnknownException when host config not exist. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in test module.
• Run mvn clean install -DskipITs to make sure unit-test pass. Run mvn clean test-compile failsafe:integration-test to make sure integration-test pass.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

[codecov-io]

Codecov Report

Merging #1491 into 2.5.x will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            2.5.x    #1491      +/-   ##
==========================================
- Coverage   28.34%   28.34%   -0.01%     
==========================================
  Files         791      791              
  Lines       41735    41735              
  Branches     8529     8529              
==========================================
- Hits        11830    11828       -2     
- Misses      27829    27833       +4     
+ Partials     2076     2074       -2

Impacted Files	Coverage Δ
...aba/dubbo/remoting/transport/mina/MinaChannel.java	42.25% <0%> (-11.27%)	⬇️
...a/dubbo/remoting/transport/netty/NettyChannel.java	61.25% <0%> (-5%)	⬇️
.../com/alibaba/dubbo/monitor/dubbo/DubboMonitor.java	73.14% <0%> (-2.78%)	⬇️
...mmon/serialize/support/dubbo/GenericDataInput.java	59.07% <0%> (+0.77%)	⬆️
...aba/dubbo/monitor/simple/SimpleMonitorService.java	52.76% <0%> (+0.85%)	⬆️
...mon/serialize/support/dubbo/GenericDataOutput.java	65.96% <0%> (+1.4%)	⬆️
...baba/dubbo/remoting/transport/mina/MinaClient.java	59.42% <0%> (+1.44%)	⬆️
...om/alibaba/dubbo/rpc/filter/ActiveLimitFilter.java	88.88% <0%> (+11.11%)	⬆️

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