415830 - jetty-start / add more TestUseCases for home + base + modules configurations

 + Adding more complexity to module persistence mechanism test case to
   demonstrate how it works.
415839 - jetty-start / warning about need for --exec given when not needed by default configuration

+ Adding exclusion on System properties check for jetty.home and jetty.base
415832 - jetty-start / fix ClassNotFound exception when starting from empty base directory

+ Displaying simple warning and not starting if appropriate.