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.

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Hi Halil,

I'd be interested to have this on Maven Central and thought I could help. I'll be happy to provide further assistance if necessary. In case you've never done it, here are directions for Maven Central:

https://docs.sonatype.org/display/Repository/Sonatype+OSS+Maven+Repository+Usage+Guide

If you like, I can also help with adding LICENSE and NOTICE files and managing license headers using the maven-license-plugin.

Reinhard