This was previously used to publish artifacts to Maven Central.
The publishing process has changed, so remove the related configuration.

Compile in java 8
Use assertj 3.x and cleanup test code
Subscription: remove test dependencies as there is no test
Upgrade maven
  - maven from 3.5.2 to 3.6.0
  - wrapper from 0.4.0 to 0.4.2
  - add maven wrapper in community

* refactor(deprecation): document replacement class to use instead

Also
  - fix class header (license part)
  - remove extra keywords in interface
  - remove useless comment