SorcerEnv: use -Dsorer.home by default and env.SORCER_HOME as failsafe
fix PropertyEvaluator default sources;
add JavaSystemProperty.ensure methods
[pom] update surefire to the latest version;
add sorcer-junit module that allows to run junit tests with running sorcer (requires sorcer to be started by the user)
migrate dbp-req main to junit/sorcer-junit tests