Optional GUI-less release using nexus-staging-maven-plugin

Add an option to perform a CLI-only release without needing to visit JBoss Nexus GUI.

The setup should follow the work done in build tools: [1] [2].

The present goal is to introduce nexus-staging-maven-plugin in a dedicated profile (let's call it release-guiless ) that would be off by default. This would allow the interested folks to use it while there would be no change for those ones who are OK with the present setup.

[1] https://github.com/hawkular/hawkular-build-tools/commit/b48133af85de156f3f7e14a68cab48704d81cb16

[2] https://github.com/hawkular/hawkular-build-tools/commit/bfe907f31ed4c4afbe9a6745303d48feda2a60f9