INGITE-4302 PR is ready for review

[Sergey Chugunov]

Hello Igniters,

I finished my work on IGNITE-4302
<https://issues.apache.org/jira/browse/IGNITE-4302> *Exchange binary
metadata with discovery custom messages*, pull request
<https://github.com/apache/ignite/pull/1506> is open, TC results
<http://ci.ignite.apache.org/viewType.html?buildTypeId=IgniteTests_RunAll&branch_IgniteTests=pull%2F1506%2Fhead&tab=buildTypeStatusDiv>
for it look good.

Please take a look; any comments and suggestions about quality of code are
welcome.

Thanks,
Sergey.