Reduce logging that is produced when building Gradle plugin

Travis is terminating builds as they are producing too much logging.
A major contributor to the volume of logging is the Gradle plugin's
build. This commit switches off debug logging for the build and
enables test event logging. This considerably reduces the volume of
logging that is produced while still providing some insight into the
build's tests.

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -23,6 +23,12 @@ jar {
 	}
 }
 
+test {
+	testLogging {
+		events "passed", "skipped", "failed"
+	}
+}
+
 eclipseJdt {
 	inputFile = rootProject.file('../../eclipse/org.eclipse.jdt.core.prefs')
 		doLast {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/pom.xml

@@ -76,7 +76,6 @@
 								<argument>${gradle.task}</argument>
 								<argument>-Pversion=${project.version}</argument>
 								<argument>-Pdescription=${project.description}</argument>
-								<argument>-d</argument>
 								<argument>-S</argument>
 							</arguments>
 						</configuration>