New repository request for igmpca

A new Gerrit repository is needed to upstream igmpca.

• The name of the repository is igmpca.
• It should be mirrored on GitHub and people should have read access on GitHub.
• igmpca is implemented in golang.  In every commit, automatic lint and syntax checking would be good. Those targets would be available in the makefile.
• Version and license checks should be automatically triggered by Jenkins.
• Users barisba and serkantul should have +2 access to the repository. The rest should be as usual. No need for any exclusions.
• We would modify the existing multicast test in the voltha-system-tests. We can define sanity test targets one we finish the integration.