Prepare for publising to Maven Central

* Inherit from org.sonatype.oss:oss-parent:7
* Add `sonatype-oss-release` in order to override plugin versions
  from parent pom
* Add `scm`, `issueManagement`, and `licenses`
* Add buildnumber-maven-plugin and enhanced configuration of the 
  maven-(jar|source|javadoc)-plugin to get proper build info into the 
  manifest.