Netflix Nebula Plugins and Gradle Versions Plugin

Changes:

• Added Netflix Nebula Gradle plugins: nebula.ospackage and nebula.release
• Added Gradle Versions Plugin, com.github.ben-manes.versions
• Tried to add Liquibase Gradle Plugin, but snapshot task conflicts with nebula.release
• Updated to and tested latest Gradle dependencies for SpringFox and Liquibase.
• Changed h2 config from local file-based db to in-memory db, for better compatibility and security