Update robotframework in testsuite to 3.2.2

Update robotframework in testsuite to 3.2.2

- declare robotframework-onap in requirements.txt and pin it's version
- add missing robotframework-jsonlibrary that is used in the ves.robot tests
- clean up deprecated syntax in Dockerfile
- improve the README formatting and add further instructions to setup
  the project and run tests
- add an initial robot_properties.py file that may contain variable declarations
  that are required to run the tests locally

Issue-ID: INT-2295
Change-Id: Ia913c610a6418643967ba1fd2791ae42038ac85e
Signed-off-by: Fiete Ostkamp <Fiete.Ostkamp@telekom.de>