[#56493992] Test tool for System API and Push API

1) Client for communicating with the Nedap Retail API
2) Based on the client, create a test-tool

The tool can be used by:
- system integrators for getting information about systems
- Nedap Retail developers for testing correct behaviour systems and API's

Source code is made open source:
https://github.com/nedap/retail-services-API

JAR should be available.