Allow case insensitive logging.level properties

Fixes gh-3356

spring-boot/src/main/java/org/springframework/boot/logging/LoggingApplicationListener.java

@@ -246,7 +246,7 @@ public class LoggingApplicationListener implements SmartApplicationListener {
 				name = null;
 			}
 			level = environment.resolvePlaceholders(level);
-			system.setLogLevel(name, LogLevel.valueOf(level));
+			system.setLogLevel(name, LogLevel.valueOf(level.toUpperCase()));
 		}
 		catch (RuntimeException ex) {
 			this.logger.error("Cannot set level: " + level + " for '" + name + "'");

spring-boot/src/test/java/org/springframework/boot/logging/LoggingApplicationListenerTests.java

@@ -210,6 +210,18 @@ public class LoggingApplicationListenerTests {
 		assertThat(this.outputCapture.toString(), containsString("testattrace"));
 	}
 
+	@Test
+	public void parseLevelsCaseInsensitive() throws Exception {
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"logging.level.org.springframework.boot=TrAcE");
+		this.initializer.initialize(this.context.getEnvironment(),
+				this.context.getClassLoader());
+		this.logger.debug("testatdebug");
+		this.logger.trace("testattrace");
+		assertThat(this.outputCapture.toString(), containsString("testatdebug"));
+		assertThat(this.outputCapture.toString(), containsString("testattrace"));
+	}
+
 	@Test
 	public void parseLevelsWithPlaceholder() throws Exception {
 		EnvironmentTestUtils.addEnvironment(this.context, "foo=TRACE",