Add a readme for the "tests" module

[lolocohen]

What do you propose?

The idea is to document in sufficient details how the tests work:

• how to run them
• what are the resulting artifacts: logs, test report, etc.
• what exactly is tested and how
• description of the accompanying scripts

Expected benefits

The hope is that:

• it will help understand how JPPF test automation works
• it will build confidence for anyone who wishes to contribute, by ensuring that changes do not break existing features, or by providing helpful feedback when things are broken