Add test description option for metadata.json

- Init smd object in constructor instead of postmortem()
- Add use of simDescription() method in example Visualization client
- Update README metadata.json example
Add simulator (infection) version to metadata.json

- Version is defined in build.gradle as well, but there doesn't seem to be
  a good way of passing the value to Java. Thus we hardcode it inside
  SimulatorMetaData class for now
- Update README metadata.json example