Make file-creation logs not resemble errors

At the first run, any missing data/config files are created
with a 'file not found' log message, which might alarm the user
as it looks like an error message.

Let's tweak the log messages to not resemble error messages.

src/main/java/seedu/address/MainApp.java

@@ -79,7 +79,7 @@ private Model initModelManager(Storage storage, ReadOnlyUserPrefs userPrefs) {
         try {
             addressBookOptional = storage.readAddressBook();
             if (!addressBookOptional.isPresent()) {
-                logger.info("Data file not found. Will be starting with a sample AddressBook");
+                logger.info("Creating a new data file populated with a sample AddressBook");
             }
             initialData = addressBookOptional.orElseGet(SampleDataUtil::getSampleAddressBook);
         } catch (DataConversionException e) {
@@ -117,6 +117,9 @@ protected Config initConfig(Path configFilePath) {
 
         try {
             Optional<Config> configOptional = ConfigUtil.readConfig(configFilePathUsed);
+            if (!configOptional.isPresent()) {
+                logger.info("Creating new config file.");
+            }
             initializedConfig = configOptional.orElse(new Config());
         } catch (DataConversionException e) {
             logger.warning("Config file at " + configFilePathUsed + " is not in the correct format. "
@@ -145,6 +148,9 @@ protected UserPrefs initPrefs(UserPrefsStorage storage) {
         UserPrefs initializedPrefs;
         try {
             Optional<UserPrefs> prefsOptional = storage.readUserPrefs();
+            if (!prefsOptional.isPresent()) {
+                logger.info("Creating new prefs file.");
+            }
             initializedPrefs = prefsOptional.orElse(new UserPrefs());
         } catch (DataConversionException e) {
             logger.warning("UserPrefs file at " + prefsFilePath + " is not in the correct format. "

src/main/java/seedu/address/commons/util/JsonUtil.java

@@ -60,9 +60,9 @@ public static <T> Optional<T> readJsonFile(
         requireNonNull(filePath);
 
         if (!Files.exists(filePath)) {
-            logger.info("Json file " + filePath + " not found");
             return Optional.empty();
         }
+        logger.info("JSON file " + filePath + " found.");
 
         T jsonFile;