Add integration tests for default launch script

This commit adds a suit of integration tests for the launch script. See
the accompanying README.adoc for further details.

Closes gh-4872

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/logback.xml

@@ -0,0 +1,13 @@
+<configuration>
+
+	<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+		<encoder>
+			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+		</encoder>
+	</appender>
+
+	<root level="INFO">
+		<appender-ref ref="STDOUT" />
+	</root>
+
+</configuration>