#605 Logger - name methods after their log level

- Remove separate print stacktrace method
- Log level into the log similar to console output

src/main/java/fr/xephi/authme/datasource/CacheDataSource.java

@@ -160,7 +160,7 @@ public class CacheDataSource implements DataSource {
         try {
             executorService.awaitTermination(5, TimeUnit.SECONDS);
         } catch (InterruptedException e) {
-            ConsoleLogger.writeStackTrace(e);
+            ConsoleLogger.logException("Could not close executor service:", e);
         }
     }