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

spring-boot-cli/testscripts/spock.groovy

@@ -0,0 +1,12 @@
+class HelloSpock extends Specification {
+    def "length of Spock's and his friends' names"() {
+        expect:
+        name.size() == length
+
+        where:
+        name     | length
+        "Spock"  | 5
+        "Kirk"   | 4
+        "Scotty" | 6
+    }
+}