Neon release [buffer]

This mainly involves all the pre-release and post-release work for ODL Neon. Once the release is approved by the TSC we have the release process as defined here [1.].

 [1.] https://docs.opendaylight.org/en/stable-fluorine/release-process/simultaneous-release.html

TSC Approval:  
RC1:
Staging repo: https://nexus.opendaylight.org/content/repositories/autorelease-2721
Signed repo: autorelease-2723
Jenkins Job Build no: https://jenkins.opendaylight.org/releng/view/autorelease/job/autorelease-release-neon-mvn35-openjdk8/40
Integration-dist: https://jenkins.opendaylight.org/releng/view/autorelease/job/integration-distribution-test-neon/185

RC2:
Staging repo: autorelease-2726
Signed repo: autorelease-2730
Jenkins Job Build no: https://jenkins.opendaylight.org/releng/view/autorelease/job/autorelease-release-neon-mvn35-openjdk8/44
Integration-dist: https://jenkins.opendaylight.org/releng/view/autorelease/job/integration-distribution-test-neon/189

RC3:
Staging repo: autorelease-2753
Signed repo: autorelease-2759
Jenkins Job Build no: https://jenkins.opendaylight.org/releng/view/autorelease/job/autorelease-release-neon-mvn35-openjdk8/56
Integration-dist: https://jenkins.opendaylight.org/releng/view/autorelease/job/integration-distribution-test-neon/201