Add 'spring test [files]' command to compile and test code automatically

- Look for JUnit test symbols, and add JUnit automatically
- Look for Spock test symbols, and add Spock automatically
- Based on what test libraries were used, invoke relevant embedded testers
  and accumulate results
- Make it so that multiple testers can be invoked through a single 'test' command
- Print out total results and write out detailed trace errors in results.txt
- Update based on the new artifact resolution mechanism